This is come up a few times before, and there’s no reason it can’t be done. See this thread for example (I think there’s others too if you have a search through the forum).
If you’re asking whether it’s only valid to use the (edited) streamlines post-SIFT, rather than directly out of tckgen, I’m not sure. But intuitively I don’t see any major issues with that – there may be minor issues with some parts of the pathway being over-represented compared to others, but I don’t think there’d be too much to worry about if you’re satisfied your pathway is well-delineated. Others may have opinions on this too… (?)