Yes sir, the Jubilee does have a bypass valve. On the Jubilee (with the original, early type oil filter) oil flows through the filter, into the hollow center bolt (which contains the bypass valve) and into the main oil gallery. If everything is working properly, the pressure at both ends of the tube is equal and the bypass valve within is closed. When the filter is clogged, pressure in the tube at the bottom of the valve is lower than the pressure at the top of the valve. When the pressure differential is approximately 7 psi the bypass valve opens. The open bypass valve allows unfiltered oil to flow into the main oil gallery under pump pressure.
There is not much to the bypass valve. Very low tech.
I am not saying that changing the oil filter wouldn't fix a low pressure situation. Under certain circumstances it might. With the later style, screw-on oil filters (the Jubilee can be retrofitted to accept the later style filters) the bypass valve is within the filter itself. If the early style oil filter with center bolt has been replaced with the later style screw on, replacing the oil filter would also replace the bypass valve. Replacing an oil filter with the early style center bolt does not affect the bypass valve, and a stuck valve/clogged filter may affect engine oil pressure.
'course, I could be wrong.