With towelette (and indeed, in some cases, vanilla) cases like these are possible:

I can see this behaviour being somewhat undesirable for certain players or modpack creators, so maybe there could be a config option added to force the creation of stone/cobblestone/obsidian blocks as if the fluidlogged blocks themselves weren't there and only the fluids are, dropping the fluidlogged blocks in question as an item as the new block is created. A similar such option could be added for ice formation.