In my Z8, hydrangeas suffer from sun scorch if exposed to the sun after 11am or 12pm. The symptoms are complete yellowing of the leaves. Only leaves in direct contact with the sun are affected though. The leaves remain yellow (including the leaf veins) for a while and then they dry out and drop.

Since your afternoon sun is dappled sun, I would try it out with one. They are in pots so you can always move them back if you see symptoms of sun scorch in the leaves.

Because of the sun intensity in the summer, you may have to limit the amt of sun still somehow. That is, they might be able to handle the sun from 1pm until 3pm in the new location. But then they may need protection from the hottest part of the day (3-5pm more or less).

All plants tend to lean towards the sun if they can help it, some more than others of course. From the plant's perspective, it is better to be where the sun hits the shrub. The problem is that too much sun could then hit the leaves during the summer and that would be bad. I notice it most on soft tissue indoor plants or on plants where the sun hits only part of the plant. You could transplant the shrub such that the sun hits the complete shrub but just make sure that the shrub gets shade around 11am. If you transplant, consider the eventual size of the shrub, not the just the current size.