Sadly, the "parker pen hours" phenomenon has been around since time immemorial . One good thing about the military background was that it was somewhat difficult to fake these things .
Apart from the fact that , on fast jets you did relatively little flying each month, (and so easy to check errors), on each of those months you filled in a total summary that was verified and signed by the squadron boss and every three months (as I recall) , it went to the base commanders office for his stamp and signature. Of course, the minions did the verification but it would be a brave chap who risked his career/neck to help out a comrade .
A military logbook could be relied on.
Sadly, I could not report the same degree of rigour once I transitioned to civil flying . I continued the old habit of monthly summary, and each year went along to the fleet office with my logbook. The nice lady put a rubber stamp on it and, if you were lucky and he was around, got the fleet captain to put his thumbprint on it. Nobody actually checked the hours I had written in.
Later on, the computerised system came in and you could get a print out to present to your next employer. The best companies demanded it , but many less enlightened outfits did not , so some "Walter Mitty" types were able to sneak in under false pretences and go on to build up legitimate hours.
The good thing is that most of these characters ( and there have been quite a few) are eventually found out . Aviation is indeed a small world , and the system will eventually weed them out, thank goodness. Most of us have seen the movie-"Catch me if you can" ; the con artists are out there , but the old adage stands--"Truth will out".
In the cockpit, when it comes down to the professional stuff, you can't hide things from your colleagues ; and then the word slowly gets around.....