Cannot pick up water source blocks while in flowing water

Description

When I am strip mining, I will often try to use a bucket of water to enter crawl mode so I can mine in a 1x1 pattern. But when I try to pick up the water, it won’t let me unless I am outside the water or my head is in the water source blocks. (Attached video)

Reproduce

Make a 2x1 tunnel, then start mining only 1 block tall on the bottom block. Place water above it to enter swim mode and go into the small tunnel. (Signs are not necessary, just for easier demonstration)

Expected Result

I should be able to pick up the water from my position and then continue mining down the tunnel.

Actual Result

I am not able to pick up the water from my position and must use a workaround like trapdoors or starting the tunnel on the top block to successfully enter the tunnel and pick up the water.