Thanks for the reminder, @spinkney.
I found the video:
and the matching paper:
https://arxiv.org/pdf/2405.07286
After equation (2), it allows range based bounds, but explicitly excludes the case where the lower bound (a) is equal to the upper bound (b), -1 \leq a_{i,j} < C_{i, j} < b_{i,j} \leq 1. The paper says it handles “known zeroes”, but I don’t see where that’s done. Wouldn’t it have to reduce the dimensionality of the inputs below n \choose 2, for example, if all the off-diagonal values were constrained to zero.