Yumiella is so unnaturally strong in fights that she's practically off the scale. So, it'd be pointless for Patrick to be evaluating that when he wants to compliment her on her efforts. Instead her obvious flaws lie in social interactions, so that's what Patrick would be looking at when she's making an effort. However, his greatest regret is that his own battle prowess is far from allowing him to stand next to Yumiella. So, what comes to his own faults, his focus would be on that. Thus if Yumiella calls him strong, he would assume she's talking about his combat strength and easily take it as a joke or sarcasm.Poor Patrick's seen and tried handling so many of her shenanigans that he can't take a compliment from her as earnest.
Yumiella should definitely take Phil out leveling XD