That's definitely not typical and is sub-standard. The undersides of both my 19 and 21 have had the same finish and shine as the topsides. There's no reason why they shouldn't have, anything pulled from a mold should be shiny and smooth.
There are two possible reasons that I can think of. One, the gelcoat wasn't cured before layup began. Happened to me on the first canoe that I ever laid up. One half looked beautiful, the other side like your bottom.
Straight to the dump.
Fortunately I learned my lesson and never had that problem again with the massive amount of f.g. work I went on to do.
The second possibility is that that part stuck in the mold and was damaged during removal. Then a remedial repair was done.
Either way, it's definitely not a typical situation.
Ron