Well, Prowl did grow up in the rough part of town, and much of the bars' clientele would have been working class - dockworkers, miners and such, in addition to the clerks and accountant-types. As a result, of course he's going to have an expanded vocabulary of oaths.

Jazz just thinks that whatever Prowl does, it's cute. Even swearing. There's a bit of a tale there too - another case: someone was kidnapping random bots and sedating them, then using them in very silly live sculptures. As part of the plan to catch the perpetrator, Prowl played bait. After the femme and her mech accomplice were arrested, Jazz found Prowl still tied up in energy-bonds in a corner of the kidnappers' "art room". Having been gagged also, when Jazz took the bonds off (starting with the gag) Prowl demonstrated his repertoire of curses.
He got very creative.
Needless to say, Jazz was impressed. Very impressed.