Here is the verbiage from the IFPA that I think would relate to "preplays" . As I mentioned in my first post I've never actually heard the term before but it just sounds like the submission of an unverified selfie score. As mentioned below, they're just used for seeding and possibly some other advantages.
"Certain formats (Selfie Leagues, TOPS Tournaments, etc) rely on players submitting their own results without the verification of a TD or authorized scorekeeper on site. Any qualifying format that includes “unverified” results where a TD, league official, or authorized scorekeeper is not present to record their score, will not have the qualifying portion included in the TGP calculation. The IFPA will classify these qualifying formats as strictly for seeding purposes, with only the finals format counting towards the TGP calculation."
You can't preplay a tournament because the IFPA requires direct competition with a Tournament Director present. This is the case for a League or Tournament where the games played will actually count towards the submission to the IFPA.
The IFPA will no longer endorse tournaments that don’t have a DIRECT play component as part of the format. DIRECT play represents multiple players (up to a max of 4) playing against one another on a given game (head-to-head or in a group).
As someone mentioned, it sounds like you're not happy with the "qualifying" portion of the league and if it doesn't have a TD, league official or authorized scorekeeper present it won't and shouldn't affect the submission to the IFPA.
Source - https://www.ifpapinball.com/menu/ranking-info/