Yeah, by default it stops at any Real and recurses over everything else.
The idea is you customise the use and ignore arguments to match your objects. These can be Union types if you need something complicated. Anything in use is taken as-is, anything in ignore is not recursed at all. Everything else is flattened until a use or ignore type is hit or there are no more child objects.
See: Flatten.jl/Flatten.jl at master · rafaqz/Flatten.jl · GitHub