Depends on your personal set of rules really. I gave up spotting in 1979 and only recorded haulage from that point on. so 90033 which was renumbered 90233 and was renumbered back to 90033 is all the same loco for me, but clearly not for others.
I am still struggling to believe these are being scrapped, but the truth is they have old hat electronics which were obsolete when built and are not economically repairable, whereas mechanical relays are more easily sourced, or repaired.
It would be nice for a class 90 to gain the "black top" livery as that suited them best, and surprised one of the LSL pair hasn't, although IO suppose the purists would say 90001 and 90002 never carried that particular variant of the livery