If you were in the aisle, you can release the armrest and have unimpeded egress.
That's what I do ... I always select aisle for long haul and release the armrest if I need to get out.
Edit: Funny note - I was on UL SIN-CMB early this year and released the armrest when I got in and out of my aisle seat. I was in 20H, which on a UL A330 is bulkhead and there was a shadow next to me. The thing about the SIN-CMB or CMB-MAA or BKK-CMB route is many speak Tamil and I'm of Tamil origin. Right across in in row 21, which is in line with row 20 (due to the closet), I overheard a wife & husband talking. Wife is sitting in the aisle seat and husband is on the middle seat of the middle 4 seats in A330. This is the translation -
Wife: "see, he (pointing at me) is able to lift the armrest, why am I not able to".
Husband: "I'm not sure, but the armrest is not movable I think, may be his armrest is broken".
Wife: "I think my seat is broken"
Husband: "It's not the seat, just the armrest. Why do you want to move the armrest anyways"
Wife: "It looks comfortable to sit without the armrest"
Husband: "The armrest is there for your comfort"
Wife: "It's not comfortable for me <Wife's voice raises>"
Husband: "Ok, wait, we can ask the FA when they come by"
Wife: "Why don't ask that guy (pointing to me)"
Husband: "No, let's wait for the FA"
Wife: "Let me ask him (again, pointing at me)"
The Husband gives in, at this point and says;
Husband: "Ok, wait, I will ask him, be calm"
The Husband then asks me what to do and I tell him that there is a small lever that can be lifted to move the armrest on aisle seats. After a few seconds of trying to find it, they were successful