I think what he means is that if you feel the need for a tiny distribution you may also feel the need for small code. And Lazarus code is rather resource intensive.
fpGui is much lighter, but also requires you to learn the whole framework and it can look rather ugly (has been improved, I believe).
MseGUI has the same caveat: you need to learn a new framework.
So if you want to stick to your LCL knowledge, don't use those two. If you want smaller code try both of these frameworks out. Both are nice. Both are stable.