The state law is clear, in PA, the deadline to receive ballots is 8 PM on election day. Any vote received after this deadline is not a legal vote, and as such should not count. The term "fraudulent" may or may not be appropriate, however, these are not votes that should be counted.
Before the election, the PA Supreme Court ruled 4-3 that "Ballots are to be treated as timely if they are postmarked on or before election day and are received within three days thereafter."
GOP asked SCOTUS to reverse it.
SCOTUS chose not to reverse it, but ordered that the ballots accepted after election day be
treated as timely and segregated in case they ended up hearing the case after the election.
The votes should be treated as valid until a judge rules them as invalid. This isn't a matter of whether or not you agree with the ruling, it's a matter of following the judges orders or not. The scenario where your argument would be valid is If the SCOTUS reversed the PA State Court ruling, and then they accepted the ballots after election day anyway.
Pretty sure it would actually be a crime if they didn't accept them as you and Trump are suggesting - can't just do what you want because you don't like how the judicial system handled it.
The last time I checked, PA election officials declined to allow poll watchers watch the ballot counting, even after a PA appellate court ordered them to. (this is a different case)
Trumps lawyers have already admitted in court, under oath, that poll watchers on behalf of the president actually were allowed in the room.
There have also been a lot of now debunked false claims involving voter fraud. I think it's likely one of those is your source.
