Well, it's not a fusion problem. The problem is with the developers of the OFX plugin.
As the name implies "open Fx", the standard is open to any developer and fusion supports that standard.
But as an developer you can build OFX plugins which will only work with specific host applications
If you stay close to the OFX standards then the plugins will work in every software
In the past fusion wasn't a huge market for developers, not many tested their products with fusion