There is that, with no proof pilots could claim anything, although you would be amazed at the, shall we say, disbelief shown towards pilots who couldn’t back up there claims.
Jammed gun cameras very often resulted in a pilot getting “nil points” on his tally, even if he had shot down 10 fighters!!! Unless another pilot backed him up, worse were kills that were not recorded ie damage that later saw the aircraft crash - not on film, not on tally. I think only one pilot was awarded two kills in the enemy fighter crashing in to a enemy bomber sceanrio, because several people saw it.
Gun film was mainly for id and int purposes, I think. It is generally believed that counts are often wildly wrong. Even the Red Baron of WW1 can only be credited with 73 definite kills (recovered wreckage on his side of the battlefield/eyewitness testimony from the victims) of his claimed 80!!!
17 could well be wrong, but at the same time, could be very accurate. Fog of War and all that.
Not too mention 109s could be confused with 190s, Stukas and 110s might be a bit harder to confuse.