This is true. So, for the sake of discussion, let's say we are talking about that front breakfall from Irimi Nage.
I like Janet's wording better.
A front breakfall from irimi nage can make martial sense if uke manages to partially free himself and turns towards nage. This happens to me as nage often enough (not so much as uke as this is not the way I usually turn if I counter).
My feeling is that the pretty breakfall from a stable standing position comes from bad habits carrying over from teching beginners how to fall. A lot of throws in aikido have very open endings where uke is launched and then has to fend for himself as nage is no longer in contact to guide the fall. This is very scary for most beginners, so we tend to let them lign themselves up, tell them to be upright and light (helps for a smooth landing as opposed to crashing in a ball, or on your head) and then we go through the motions of throwing them.
Then we trade places and much the same happens with the advanced person as uke since the beginner has little hope of pulling off a real throw, we position ourselves to fall and go through the motions.
This isn't so bad for a start. But if you are still doing this with more advanced students (say anybody fourth kyu and up), then your pretty much just dancing, each person taking turns being the lead.
One thing I try to do to avoid this trap is that when just going through the motions, I put myself in an unbalanced, about to fall position and try to have the learning nage place themselve in a position to do the final push just as if they had got me there against my will. When it's my time as nage I have more trouble, it's really hard to throw someone outwards and have them land safely if they don't yet have the skill to land or roll safely (I've sent a few beginners flat onto their backs or stumbling into the walls, which I really try to avoid). Mostly you have to stop and let them take self controlled ukemi and wait until they get better.