It was 100 hrs in the preceding 12 months for many years at many big regionals, but I believe times have changed. I have heard stories of failures for folks who show up woefully rusty, so it might be worth getting some time to take the rust off. Would you rather put your family in a plane with a pilot who hadn’t flown in 5 years, or one who has been logging 60-70 + hrs a month for the last 5 years?

Strawman argument? No legacy hires or flies someone with zero flying in five years. Regional airlines may do it, but with an LCA during IOE and they are only signed off once they're proficient. Your point that a regional airline pilot with 3900 hours in the past five years may have a lot less rust than, say, a military pilot who hasn't flown for the last five years of their career is valid. But both pilots are likely training on a new type aircraft and need to be vetted and certified.