I think the insinuation there might have been he'd actually gone back in time as a result of testing his powers and finding out things got weird the closer he got to light speed. Pairing with how the CW show handled some time travel, could probably say he "merged" with his past Barry and was thus at pre-origin life situation, just with powers. Unfortunately paradoxical, but that's also something they handwaved from time to time. Could also emphasize his creeper status on Iris since he would've known her, but had to act like he wouldn't out of bullet time.