Yes, it's an opposite scenario.
On a relatively recent occasion when Reading passengers were reportedly overcarried to Swindon, they were not charged and allowed to travel back to Reading for free.
Some people appeared to be extremely upset that GWR allowed this, which was perhaps even more amusing than the original incident.
Yes that was the case in my experience travelling earlier this year on the 1912 Paddington to Bristol HST . It's first stop on Mon to Thursday was Swindon. Guards announced several times that this train does not stop at Reading but each time despite announcements there were quite a few Reading passengers.
The Guard and buffet crew just advised taking the next train back to Reading from Swindon at no charge.
I think that attitude from staff is the best of customer service the railway provides despite being the passengers fault.
BTW it was an experience to pass through Reading at 50mph non stop!