I've never worked anywhere where I could randomly decide if "full time" was 40 hours a week or 30 hours a week.
What the hell does it matter??
If my employer says "you're full time, which means you work 40 hours a week" I can't just say "lol, I'm salaried, I do what I want, fuck you." nor can I say "lol, I get to choose my hours because I'm hourly, I only feel like getting paid for 30 hours a week, fuck you."
That's an extreme form of insubordination and it almost certainly means immediate dismissal.
I've had five software jobs.
But it really depends on the company, I worked in both scenarios. Sometimes I can't broker a better deal or find a better company and again, a good team or an exciting project may make up for dickhead management and their paranoid lack of trust.
("Enterprise" and "charging CLINs" are hardly the same thing)