It was at this moment that he knew he f**ked up

Then what was he doing...?

Ochaco.....I'm sorry I'm sorry I'm sorry

…

Understandable, have a great day.

But legitimately, what exactly could Deku have been doing? This is clearly post-"Moving Into Dorms", so why is Deku supposed to be at his mom's? Also, Deku isn't exactly the type to break curfew. He did so once, and that was to help Bakugo out.

I DONT know, honestly😂maybe he and Iida were chaperoning Kaminari and Kirishima to a movie🤷

Prepare for advanced fan theory: This is clearly post-"Moving into Dorms" since All Might is in front of Deku's mom in his weak form, but the only time Deku visited his mom after that episode (as far as I know) was in the Christmas episode. That means that this cannot canonically take place in the current canon. I therefore hypothesize that the only time that this could take place is at some point after season 6. So, I guess your joke might not be too far off the mark, because maybe they actually started dating post-season 6.
(NOTICE: I do not read the manga, and since I watch dubs, I've only watched about halfway through season 6. Some information may be invalid.)

Correction: he last visited his mom (as far as I know) for New Year's, shortly before he started his work study at the Endeavor Agency.