@Guvnor, @littleKAF and @Halifax have already pointed out that this is incorrect, and each Summon within a 10 pull has the same possibility of getting a HOTM Bonus Draw as a single Summon done alone would.
But I wanted to add on that this is also incorrect about how the Atlantis Bonus Chest works. A 10 or 30 pull there will count toward the Bonus Chest as 10 or 30 Summons too, up to the cap of opening 9 Bonus Chests per month, just like individual Summons would allow for.
There is absolutely no functional difference between multi-pulls and single pulls.
They work simply as a series of individual Summons, all executed back to back.
But there is one modest advantage to single Summons over 10- and 30-pulls: you can stop if you get what you want.
That’s not typically a good reason to spend the higher gem cost if you intend to Summon more anyway, as it’ll just cost more, but it is a good reason to use Epic Hero Tokens/Atlantis Coins/Challenge Coins individually before you use gems for 10- or 30-pulls, in case you get what you wanted and can stop.
Also, as with all discussions of Summoning, I’d like to remind anyone reading this to please set and stick to a budget, and please consider reading or re-reading these excellent threads:
If you’ve read them a million times before, you may consider reading them again before deciding on your budget for summoning. A little time spent deciding on how much money you want to risk on summoning goes a long way to avoiding disappointment, frustration, and regret later. 