They were not referred to as "Tanto" tips, but bowhunters have been rounding, squaring and otherwise losing the pointed tip on broadheads for years. I am not certain that it helps in penetration (not certain it doesn't either)but it makes a ton of sense that it offers a stronger tip and...
we have often seen that once a tip starts to bend over, it goes.. period. To keep a tip from bending, don't let it start. Same idea as a straw in a storm, or an arrow into anything. Straight on it is strong, on an angle... well, not so strong.
I say... if it makes you feel like it is a good thing.. certainy do it.
ChuckC