It’s time for a serious explanation. That’s one massive false advertisement.
"Increased chance for Legendary Hero"
Clarify terminology used in probability tables (poll added)
There is an increased chance, the +1% of an event 5*. If you count the % you see that the event chances are in addition of the normal hero chances.
You’re comparing “Epic” to “Event”. Look at “Elemental”.
Edit: Sorry, I’m being unclear. There are two different things happening here.

For Elemental summons (not available during events), the chance of drawing a legendary hero is explicitly increased.

For Event summons, the base chance of drawing a legendary hero is the same, but then you get an improved draw chance with an increased probability of pulling a legendary hero (and an epic hero). That is all totally consistent with previous wording.
That is not what it says. Wording is very important. If this was McDonald’s they would be handing out free six packs of legendary heroes right now to avoid a lawsuit.
Legendary Hero 1,5% + Legendary Event Hero 1% = 2,5%
It is higher than Epic Hero Summons.
They both read the same. Let me just go pull up elem, wait, you know that you can’t pull up elemental summons during an event. You are just being argumentative so why even comment? You honestly should know better.
I think my previous answer was unclear so I’ve edited it. I’m not being argumentative here, I’m explaining something that I think is pretty obvious. You should not feel ashamed for not understanding it, but you should feel ashamed for assuming I’m being argumentative. I’m not: I’m being lovely.
Then it should read “Bonus chance at Legendary Event Hero” or something a long those lines. You are missing the fact that they split the Legendary Hero pulls into two separate dismal chances. There is no increased chance, they are not additive. There is a 1% and a 1.5%. That’s not an increased chance, that’s another chance, it’s a lie and it’s false advertising.
That absolutely is an increased chance. If you don’t understand that then you don’t understand how probabilities work.
I do understand it. It’s not an increased chance, it’s another chance. I would take a 3% chance over 3 one percent chances 7 days a week because the odds are 3 times as likely to hit in that 3% than that 1%. It’s okay if you don’t understand odds and chances. It’s been worded one way forever and when the details are released it turns out it doesn’t work the way it was worded.
 You clearly don’t understand it. Maybe it’s my wording that is the problem, so I’ve reworded again.
 The app is explaining your additional chance of drawing a legendary hero. I do not see what you do not understand about this.
 Would you like to illustrate how you think it works with some maths, so we can explain how you are wrong? That might be easiest.
You must be another one that doesn’t understand odds. Take a dice with one hundred sides, try to roll a 13, you are three times more likely to hit 13 in one roll than 1 in 3 rolls. The wording has always described the former when it is actually the latter. That is an additional chance, not increased.
Maybe you guys don’t speak English as your native language so I’m giving you the benefit of the doubt. We are discussing language and the difference between additional and increased as it pertains to chance odds.
English is indeed my native language. I hope it is yours, too.
On a D100, what is a “13”? Do you mean rolling a “13” or something else? You might need to work on your terminology.
Once again the game says “increased” not “additional”. I agree there is an additional chance, the chance however is not increased.
But the case here is that on a roll of 1 you get an event 5*, and on roll of 2 and 3 you get a normal 5*, so you get a 5* with all rolls of 13. Hence, increased chance.
One through three. Do you need further clarification or should I provide the dictionary definitions of additional and increased so we can get on the same page. I didn’t write the advertisement or invent the English language, I merely understand what it says. When read in plain English it says something different than the new information provided.
The “additional” chance (it’s not described as such, btw) does not apply to the bonus roll (though if it did, that would indeed “increase” the chance of drawing a legendary hero). The “additional” chance refers to the improvement in odds of drawing a legendary (and epic) hero over the base chance.
A legendary event hero is a legendary hero. So when pulling in event summon you have 2,5% chance to get a legendary hero. As you have only 1,5% in a normal pull and as 2,5% is greater than 1,5% they are correct and you are wrong.