You just need more force, sometimes the front group is threaded in really tight, or seized. There are a few lenses that I was not able to disassemble, it is possible that some prior service may have added an inappropriate thread lock compound.
The worse lens (that I really wanted to dismantle) - I set up the lens spanner in a vise with appropriate support such that I could apply torque to the body using an oil filter tool to unscrew the front group. It was pretty messy.
Hasselblad optical blocks are pretty easy to remove, so dust and fungus on the outside of the optical blocks are usually easy to clean. If you get one that still has a lot of dust or fungus, then there is a chance that the optical block is seized (or just really tight).
If the fungus is inside the front block, you will have to disassemble the block after it is removed.