Originally Posted by jsloan

There is no such bonus on “preferred partners,” at least not if by “preferred partners” you mean “partners that earn PQP at a 5:1 ratio instead of 6:1”. Rather, each airline can elect to offer such a bonus or not. For whatever reason, at the moment, Lufthansa does, but Swiss does not, despite being part of the same ownership group. You can find this information on the page for each partner: compare Swiss to Lufthansa, and note how the latter includes the phrase “Premier members can earn Premier Bonus award miles” whereas the former does not.

The PQP calculator referenced elsewhere in this thread does include bonus miles for Swiss flights, so this is presumably a recent (and unwelcome) change.