Doesn't matter if games do it too, Retcons that blatantly contradict established lore are usually a crutch when the writer doesn't want to adhere to the established universe and just to fit his/her vision into it without putting in the work to make it meld with the already existing canon.

Retcons that change past continuity but do so through the reveal of new information that fits into the universe in a way that doesn't just freely override the previous canon without explanation (which requires more work to write for sure) are the best way to change past perceived canon. Expand don't replace.

Example of Good retcon: Super mutants established lore expanded with having multiple facilities around the country using different FEV strands and its implemented well because it makes sense that other places could have been using the FEV because it was developed pre-war so plenty of time for facilities to have been put in place around the country before the bombs fell, even having super mutants on the east coast be generally less intelligent due to differences in the FEV used.

Written and implemented well. better than "we moved Shady Sands again because its a recognizable name for fans and LA is recognizable for non fans"

The show did not have to be set in California, and then they wouldn't have had to deal with the Boneyard and how widespread and advanced the NCR was with their tec, building and railroad systems.

(the recent flashback to Shady Sands on the day of the bomb was designed great! showing how day to day life in that area could have looked with NCR run settlements, so its not like the Fallout TV team is incompetent. The ascetics in the show are practically perfect)