Flip side: One of my older brothers graduated high school in California, and enlisted in the USAF. He was sent to Texas for training, then back to Europe.
He came back to Texas a couple of times for stateside duty & further training, always returning to Europe.
He bought & kept a house & car in Texas; obtained a Texas drivers license, etc.
Went back to Europe, then finally retired, after 20 years, requesting & recieving his discharge in Texas, where he still owned his property.
California filed liens for unfiled state taxes, from the time he changed his residency to Texas, until the time he retired, on the basis that he enlisted as a California resident, so he remained a California resident, and COULD NOT change said residency, until returning to the state to be discharged, THEN moving out of state as a civilian.
Oh, yes; they also felt entitled to part of his retirement pay, since he had earned it 'while a California resident'.
I left in '84, and haven't looked back; I also converted my retirement fund to cash when I left, so they wouldn't have future claims against me. That money helped finance the move, by making up most of my Jimmahcarterization losses. If Reagan hadn't won, I'd still be trying to earn my way out of that Hell-hole.
IIRC the California Tax Gestapo is called “The State Board of Equalization.” Now there is truth in advertising. I had a situation somewhat similar to your friend. I had to hire a bad a$$ CA tax attorney to call the state’s bluff; they folded like the proverbial house of cards.
I did exactly the same thing. I was a Virginia resident and didn't want to pay state taxes so when I reported to flight school in P'cola I changed my residency to Florida, which at the time cost me $350 in taxes on my car. I left Florida after about a year and never went back, but maintained my residency until I got off active duty.
The best fringe benefit from that was casting an absentee ballot in 2000 for George Bush.