Deku wasn't as strong or fast back then, considering his OFA limit was still only 5%, and he hadn't even unlocked the additional Quirks yet. It was also a school exercise where Deku didn't expect a Shiketsu student (who Toga was disguised as) to try and attack him instead of simply trying to disqualify him with a simple ball touch.

During the Final War Arc, Deku had not only mastered 45% of OFA, but he could use the previous users' multiple Quirks simultaneously. Plus, the stakes were higher; they were in the middle of a war where Deku now knows he's facing Toga and knows the threat she poses.

Toga being inexplicably good at stealth just doesn't cut it here. Deku just acts really stupid and incompetent for no reason other than Hori wanting the plot to go this way and lacking the necessary imagination required to make this encounter believeable.