Nice video explanation.
In essence, in terms of tile dmg, the whole is more than the sum of the parts when you use mono. This, along with the advantage of high post-mortem tile dmg like you mentioned, allows one to take down players with much stronger defenses.
In war, I typically bring mono teams (with some 4* heroes) that are ~3600-4000 Total Power against defenses that are 4500-4700+ TP and have a decent win percentage. However, as I build my roster, I am gradually shifting some of my teams to 4-1.
I think that there is a balance between mana efficiency and probability of making matches in your color. In your case, because you have multiple leveled troops and team synergy, mono can work well with a decently high win percentage. However, I am not convinced that mono teams are superior to 4-1 in terms of long term win percentage. One would have to do an extensive statistical analysis with many set controls to make that conclusion (not saying that you made that conclusion).
In the example you gave at 14:45 in the video about mana inefficiency with 4-1, mana inefficiency is not a factor towards winning in that scenario. It’s not important to have the maximal mana efficiency in that case because the tile dmg of 4 greens is enough and you were also able to charge 4 specials at once which is enough to win the battle. If you were to bring a mono green against that defense and have only few green tiles on the board, there is a higher chance that you would’ve lost compared to if you had a bad board with 4-1. On a starting board with few green tiles in 4-1, you have a higher chance of making 3 yellow matches and firing Mist, which would slow down the defenders and give you a few more moves to work the board. You want to ideally have a balance between mana efficiency and probability of making matches of your color(s) to create the optimal win probability.
I think you did a good job in explaining how mono works well for you in the video.
Also, I would HIGHLY discourage using mono teams in rush attack wars.