Not long ago there was a case in the States of some clown who had more hours than required for the rating applied for, but ALSO had some falsified hours in his logbook. He attempted to defend himself on the basis that the falsified hours made no difference but he was crucified on the simple basis that he had made false entries in the logbook. I think the FAA revoked his license, with a two-year ban on even re-applying for it. He appealed and lost, when the case made the aviation news.
Not many people pay close attention to it but check out the bottom line on any application for a medical, a license or a rating. It means just what it says, as that fellow found out.
Your 'friend' should probably think about swapping that falsified logbook for another one with only correct entries. It would be a lot less trouble than leaving that paper trail out there to be discovered some day.
You ever notice how most logbooks are rather well-made? Pages bound in 'signatures' and, often, numbered, so that you cannot just snip a page out without that being obvious. Why might that be?
Crazy stuff happens: There was an airline pilot who overlooked a timely renewal of his medical and then decided to just carry on without it. Finally a flight deck inspection caught up with him after a couple of years, when, of course, all hell broke loose. You could probably sum up this sort of thing by saying that it must have seemed like a good idea at the time.