Tri bikes with the larger seat angles use a different set of muscles than a normal bike - You pedal more with your quads on a tri bike. Whereas a regular bike uses your quads and hamstrings.

So a tri bike saves your hamstrings for running.

I'm 5'1 - I like a 73 degree seat angle on my bikes... that seems to be where I'm comfortable & pedal efficiently. I've had 74 & 73.5 degree seat angle bikes and they always seem to make me hang my butt off the back of the seat to get comfortable.

my surly has like a 75 degree seat angle... and I'm getting used to it, but don't like it for long distances, I end up hanging my butt off the end of the seat.

They put larger seat angles on smaller bikes to shorten the top tube & reach for smaller riders...