I think the meaning behind this is that they would expect Biden to not challenge the result similar to what Trump is doing now.
That's exactly the problem then, isn't it? Stake is willing to pay out a Biden bet despite a dispute from Trump, but perhaps wouldn't pay out a Trump bet if there was a dispute from Biden per that interpretation.
I doubt that you will face any problem at all aside from the fact that your provider will pay you in February (from your own account ) while you are paying right now, that is the only thing that you are going to miss out, few months of not getting paid for something you should be getting paid for and that's it.
We have seen tens of cases Trump campaign has already getting rejected, they have ZERO proof that anything could go own their way, people keep claiming "let's wait for the courts!" but the reality is, courts are not even accepting his plea, so at the end of the day we do not even have to wait for Trump to win any court case because those cases are not even being heard let alone get a decision in the end. So, Biden win is 100% guaranteed at this point, only thing stake loses right now would be not getting paid for few months.