As you can see in Attachment 1, the water flow direction doesn't get blocked by structure void which breaks water transportation systems for players based on structure void blocks, but it works with signs just normally.

To reproduce the issue, just build a construction like in Attachment 1 with one using signs and one using structure void. Then observe the flow direction of the structure void one to be incorrect.

I also searched for issues that are possibly referencing this issue and have found nothing. If I did miss one, sorry

Attachment 1: