Which flagships?
Samsung have so many "flagship" devices it's embarrassing.
I had a "flagship" Note 12.2 Pro that still had 4.4.2 when I sold it recently.
My "flagship" Galaxy Note 4 is still on 4.4.2 as the version 5 upgrade is a disaster and overheats the device whilst killing the battery.
My "flagship" Tab S 8.4 is on 5.0.2 and seems to work sort of OK
Samsung are a disaster and I'm done with them. Too many devices, no roadmap and crap support.