I've been led to believe that there are brokers who have information on your employment history and that it will likely show up in a background check. Famously, employment dates are the only thing a typical HR department will give out when cold called by a potential new employer. Basically, it's not something I'd fluff beyond a month or two. I'd find something else to fill a big gap on a resume if needed (sabbatical, volunteering, consulting, whatever) just in case it's something that an automated filter is tossing out.

Yes if it gets to filling out background check documents, I don't fudge dates. I have though typically only needed to do those after offer has been made, etc.

I sometimes don't update LinkedIn for years. Sometimes I get calls from recruiters who think I'm still at a previous company.