Ok, so I got this great job with a lot of career growth and nice pay increase. My reason for leaving was hitting a glass ceiling, I couldn't grow much in my position, and yeah, the new job pay was also tempting.

So I told my director the main reason career growth. He tries to counter offer but I shut that door cos I guess once you show your hand you're labeled "disloyal". Now when you quit you get an exit interview with HR, he wants me to say I wasn't happy I didn't get paid overtime (as a senior staff I am exempted from such pay, but did LOTS of overtime), coz he wants to use that to help the rest of the team,

Now even though I didn't get paid, I knew this when I joined, and it wasn't on the top 5 reasons I left, should I lie and take this for the team?

I heard to try and be vague and not hover around money in your exit interview as your reason for leaving so when your file is ever called up in the future (e.g. u need a reference) it makes you look professional if you left for a reason such as career growth.

It is probably not your duty to sacrifice your reputation for the sake of a team you are no longer a part of.

And let's not forget telling a lie might come back to bite you. There's little to gain and much to lose.

Since he's no longer your boss, you don't need his approval anymore. So I think it would be a mistake to tell this lie.