Molded fiberglass comes from the factory with a gelcoat finish, a thin surface layer of glossy resin. It can be colored, and it is cosmetic, not structural. No paint
Over time, if unprotected from the sun, it deteriorates from UV exposure, becoming thinner and chalky. In early stages it can be restored with polishing and a good wax. For extreme UV weathering, floor wax is an alternative. A high gloss finish on an older trailer is likely floor wax. It has to be stripped and reapplied periodically, though typically not as often as regular automotive or marine wax.
However, if fiberglass repairs are made- holes filled, cracks patched- the original finish cannot be easily restored. Gelcoat restoration is possible ($$$), but for a small egg trailer, paint is the most practical way to restore a like-new surface appearance following fiberglass repair.
Well-done fiberglass repairs are as good as (or in some cases, better then) new. That's one of the great things about molded shells. However, it is always possible someone has just smeared Bondo on a structural crack, sanded and painted without making a proper fiberglass repair. The quality of the paint job could be one indication of the quality of the underlying repair work. In my mind it would be a reason to ask some pointed questions of a seller.