Like the other characters said, it was all in theory that the drug erases their memories completely. I'm pretty sure it masks those memories to that extent but can't erase it. It's like if you see something familiar and you feel like you should know it but doesn't come back. It's been occurred many moments after the experiment ended and why after urging these familiarity enough, it'll bring back those memories. It is a new drug after all and made in secret so there are many things even the scientists are unaware of
So there really are no discrepancies made I believe ^^
I'm so glad it brought back to everything Arata wasn't able to do during the confession and their last moments in ReLife T_T Right when he recognized Hishiro, he immediately asked to date her and even kissed her (ask me again when you're an adult). You're really not holding back like you said huh Arata?
Also I agree, Hishiron is completely right in saying he's good at meddling
Also Yoake and An :3 Guess it's the defining trait in order to be a support