It isn’t just an issue of the prostate shrinking. The attached article points out that there is atrophy (tissue wasting) and apoptosis (cell death) in the prostate as well. You can do a quick Google search to see that there are hundreds of thousands of guys who have used Propecia and despite stopping the drug, still report having watery semen with reduced volumes.
Yes, I don’t doubt that for a moment. I know of one family member that stopped Finasteride after 15 years and had a full return of his semen to its normal level and consistency, so that means that the results vary with people.