Yes of course if flawless block fails it will be a problem. Same with S1 interrupt.I would say the flawless block can be a risky option as well. You block too early, hes plus and can do virtually whatever he wants, you block to late and he gets a full combo.
Using nut kick as a reversal is indeed risky but if it works, you turned the tables and now you're plus and he has to hold your follow up.
Not the liu kang player has 2 options he has to think about, a plus nut kick reversal that puts him at the mercy of plus frames and a flawless block that leads to a juggle.
2 options are way better then one lol
Nut kick can be executed much easier.
And I agree that one more option is always better.
Next time I play a Liu I will try it. At least I do not have to care about execution.
But I try to play and focus on the more difficult but more optimal solutions.
Flawless block can cover several Liu's follow up as well (special cancels) while nut kick interrupt covers stagger (except block).
S1 interrupt is more rewarding than nut kick and covers block but weak against D1/D2 stagger.
F4 stagger will win lol.
In Kombat league I play against low-mid skill players (I believe myself as mid) so probably it will work too.
I just always try to play better and use more advanced options if possible despite the opponent and my general skill and fg level.