I personally have never owned FT's or done any work on FT's but from what I understand the problem with footbeds (or insoles) in FT is the FT liners bottom part which your foot sits on is soft, unlike most liners which makes it hard to get the footbed in the right position. I think it is soft because FT don't actually come with any kind of footbed or insole, supposedly the liner of the boot will mold to your foot (it won't actually truly do this though). It is more difficult to get the footbed to sit squarely in place, if the footbed isn't in the right position then it isn't really going to achieve anything because your foot will still be mispositioned.
I have never seen those footbeds before, did you get them molded to your foot or did they just come in a certain shape already and you just put them into the liner?
If they are what you call trim to fits, meaning they come in a certain shape already and you just trim them down to fit into the boot then they won't be optimal. Yes they will probably be better than no footbed if they're in the liner properly but they won't provide the support of a fully custom footbed. Ideally you want to get a full custom molded footbed that is unique to your feet.