If you launch the game with space.exe out of the box, the game is preset to use 3Dfx Glide. However, in some environments like Wineskin or PlayOnMac (I can't speak to PoL, but I would reckon it's similar to PlayOnMac, given that it's based off of PlayOnLinux), the user is asked to point to an .exe to be used to launch the game. Immediately it's not made clear to the user what .exe to use: space.exe or Tachyon.exe?
This state of affairs is common for a lot of games that use both dedicated launcher .exes and .exes for the actual game itself. Civilization III Complete is one such game. There is a dedicated launcher for the game that in my experience, doesn't seem to work (even if you install dotNET, which is what it seems to ask for in the Wine error log). However, the game works if you launch it from the Conquests folder. IIRC Paradox's grand strategy games also have a similar setup too.
If a prospective user elected to use Tachyon.exe (a reasonable guess), then the game would be set to use Direct3D. What may further lead to confusion is that in a lot of cases, 3Dfx Glide is either employed through the use of a custom .exe explicitly labelled as a 3Dfx version, or 3Dfx is offered as a rendering option in the game's launcher. For whatever reason, Tachyon has neither of these.
In any case, I think posting the links to the instructions on Steam was perfectly reasonable, given that some users may have tried launching the game through Tachyon.exe and may be left wondering why 3Dfx isn't available, or may be unaware that there is a better way to run the game than the laggy Direct3D renderer.
Is there a way to make IL-2 Sturmovik 1946 run on Wine with Mods? I use the Wine Wrapper from PaulTheTall to run the base game and it works propperly. But when I install the HSFX or the Ultra Pack Mod, the game won't start anymore.
Have you checked your Wine log? Perhaps those mods have dependencies you may not have.