Well, yes. We'll risk the $100 bill vs. not being paid at all.
The point stands that, in my experience, $100 bills are an outlier in most of the US and will, at a minimum, invite additional scrutiny or simply be refused in many situations.
If you insist, they could take me to court for not paying the bill, at which time they'd have to accept USD for the debt.
So yes, they could refuse the $100 and then sue me, at which point they'd have to take it. So you'd get a big clap for technically "winning" this argument but in possibly the dumbest way possible.
In practice, the reason why 'legal tender for all debts' is relevant is because it pretty much forces to take my $100 or go through an expensive process to just end up with the same result.
Legal tender for all debts.