I think their rationale was that Penix is QB1 in the typical draft and with Cousins the Falcons won't be picking highly enough to draft a QB1 before his deal is over. Penix gets to learn behind Cousins and insure against injury or carryover from the Achilles injury. Mahomes sat 2ish years, so did Love so that part is not unprecedented it just means less rookie deal run--not insurmountable. Yeah he will be 27 by the time he is forecast to take over as the starter, but he would still have 8-10 years of functional play left and that's plenty worth the investment.I wanna go on record and say, I think what they did was smart. Penix was my #3 QB in this draft and Cousins is old and is a choke artist.
My initial reaction was also wtf but after hearing more viewpoints I think there is good logic to what the Falcons did.