Yes, that practice certainly goes on.
Many registrars "automatically" assign a +1-year expiration date to an expired domain name. This is done, IMNHO, to confuse the innocents.
Usually/many times, there are two expiration dates listed in a whois record -- the one nearest the top of the record shows the "plus 1-year" date, and the expiration date closest to the bottom of the record shows the "real" expiration date.
AFAIK, the spurious "plus 1-year" date is put in place by the REGISTRAR -- not the registry.
If you take the time to read the [cough] "information" that accompanies many whois results, you'll often find a long paragraph of absurd language that, in essence, says "the expiration date shown is the expiration date -- unless it's not."
This misinformation, in my view, is to allow REGI$TRAR$ to (more easily) move the expired domain to their own (partner) auction market.