could this have begun as a severe case of get-homeitis?
It could equally have been a pragmatic approach to getting out of GIG in the first place. I haven't seen the performance figures for the flight but they may not have been able to lift the planned payload and "full" GIG-CDG fuel out of GIG...they might have been able to carry fuel for GIG-CDG plus a little bit of extra, but not enough to give them the legal amount of contingency, or buffer fuel, needed at the
start of the flight. One option would be to come back on a windier cooler day, another dump freight or passengers...
, another one would be to fill up as much as possible, file a plan for say GIG-TLS - which given the shorter track could then mean you have full legal contigency fuel for that sector, so all legal, above board, a recognised procedure and safe.
Once you approach TLS you look again at fuel on board and decide wether you have enough in tanks to overfly TLS and continue to CDG
with legal reserves or wether you don't, in which case have to do a tech stop.
It's not a technique used as much these days as it was 20-30 years ago but it still has it's uses if you're short of performance, and it's perfectly legal, the critical thing is you don't press on beyond the en-route alternate without fuel to so so....sadly the crew of AF447 never got to make that decision.
SoaringTS...you beat me to it, Rgds.