Water does not flow into space after breaking a glass block in an underwater base on Realms

In my Realm, my friend built an underwater base using glass blocks as walls. When breaking one of the glass blocks, we expected the surrounding ocean water to flow into the empty space, as it normally does in Minecraft. However, the water did not flow in. There were no sponges or commands preventing the water — it simply did not update, as if the glass block was still there.

This caused confusion among Realm players, as we thought someone was using commands or tricks to block water flow, which led to unnecessary arguments.

This seems to be a bug.