The creator of the format, Steve Wihite, says it’s pronounced as JIF, but personally I still say GIF out of habit.
https://www.cnn.com/2013/05/22/tech/web/pronounce-gif/index.html
I’ve had similar arguments with people over the pronunciation of Linux, with one person saying it’s “Lie-nicks” because it’s named after “Linus”, but Linus himself has said he pronounces his own name differently depending on the language he’s speaking at the time, but Linux is always pronounced “Lynn-icks.”
It’s like hearing people who work at Asus call it Asus instead of Asus.
The only reason they’re saying it’s Asus is because they have to. They say Asus like everyone else at home.
Also, after a certain amount of time, the word you made up is no longer yours. That be how language works yo.