Answer
Do APC waivers apply to hybrid journals?
Almost never. Of fifteen publishers checked, only IOP Publishing states that its discounts apply equally to fully open access and hybrid open access journals. Elsevier, Wiley, Taylor & Francis, Sage, Oxford and BMC all limit waivers to fully open access titles. The stated reason is that authors can publish in a hybrid journal at no cost via the subscription route.
Detail
When the exclusion actually hurts
If your funder requires immediate open access, the subscription route is closed to you, and the hybrid exclusion becomes a real barrier rather than a theoretical one.