For sure, it would be rude if the party specification was for multiple runs. My reply was in response to people saying that some players don't want to use the PF because they don't want to be obligated to do multiple runs -- my point is that they can use PF without that obligation. Parties in party finder can specify that they only want to do a single run, and there are people who currently do use it that way. It's not rude to leave after one run if the party comment states that the party is only going to do one run.