"This cuts the biscuit" isn't a well-known phrase. I can only find two examples on Google, one is quoted in the question and the other is:
I understand it happening in earlier chappys but this cuts the biscuit but all suggestions aside this is the best yet.
There's nothing else in Google Books or Google Groups, so guessing from the context alone it sounds like it means something is above expectations.
It's probably a confusion of "take the biscuit":
(idiomati, UK) To be particularly bad, objectionable, or egregious.
I've seen bad grammar, but this takes the biscuit.
(idiomatic, Canada) To be of no further use; to be near death.
(to be particularly egregious): take the cake (US):
(to be of no further use): have the biscuit (Canada):
And "cut the mustard":
(idiomatic) To suffice; to be good or effective enough.
Give me the bigger hammer. This little one just doesn't cut the mustard.
This idiom usually appears in negative polarity contexts: “doesn't cut the mustard”, “can't cut the mustard”, and so on.
The slang Urban Dictionary defines let's cut this biscuit as:
A phrase that is used used to signal, perhaps impatiently, a desire for something to begin. It could be a project, a trip, asking someone out--anything for which preparations have been made, and a specific goal is to be achieved.
1. "All right people, let's cut this biscuit!"
2. A: "So you ready to hit the party? Jenna's going to be there, you know."
B: "Yeah, man, let's cut this biscuit."
However, it was defined in 2007 and is the only definition, with only 16 upvotes and 4 downvotes, showing it's not very common at all.