I don't agree. Zig allocators require the size of the allocation (technically they take a slice, but a slice is ptr + size), as does the C++ polymorphic allocator, as does many allocator interfaces in many libraries (see for instance the allocator interface in Lua, my personal favorite C interface for memory allocation [0]). Clearly having it as a correctness requirement works just fine.

[0]: https://www.lua.org/manual/5.4/manual.html#lua_Alloc