I owned a WTRP and my experience was that the stretchier the belt the heavier weight oil was optimal. When I had my original stiff belt or the mostly OEM Stanalog replacements, the then recommended 50W motor oil worked great. When George went out of business, only stretchier belts were available and 90W gear oil made them tolerable. When I was finally patient enough to make a proper string drive, then 5W mineral oil helped the string not to slip but didn't raise the bearing noise level.
Not sure of the current state of belt availability for WT tables, so YMMV. If Bill has OEM belts as replacements, then you should definitely follow his oil recommendation.
David