Yes, you are correct.
The maximum FSB is what the CPU can achieve and that would be 533.
P4 motherboards come in 4 different flavors that I am aware of:
1. 400FSB
2. 400, 533FSB
3. 400,533, 800FSB
4. 800FSB
A CPU usually can go slower if need be, i.e. 533 cpu on a 400 motherboard.
But you can't force a cpu to run 800 if the cpu itself is only 533.
Hope this answers your question.