Manchester United this season do always have good performance against big teams, that is why I expected them to get at least a point in this match just as they did against Chelsea and luckily it worked because as an Arsenal fan I am happy with the outcome of the result because Arsenal has now gone back to the top of the Premier League table with one point difference. Now only match between Arsenal and Liverpool at Anfield will determine their respective position but I will also expect a draw in the match since Arsenal and Liverpool will not always wants to lose.
Manchester united did had an average performance today probably because they have left the champion's league and were also unable to make it to the Europa so they are giving their very best to at least finish top four so they can get an appearance in next seasons UCL. Onana did made some good saves today that did appear a bit impressive.
I agree with you that Manchester united have most often showed this level of resistance with bigger teams trying to make sure they steal a point from them but if they meet average teams they tend to just be complacent and loose in some cases. Arsenal getting back to the top of the table is a good one for them but they must not lay down their guards as they are just one point away from the team at second position which means with a win Liverpool could be back at the top of the table again but I think Arsenal is beginning to have a better chance at the league title than with others on the table.