The table saw jig is used for trimming the the spars to the correct length. I recommend leaving the rib blanks all the same length and only trimming for cap strips just before assembly. The ribs are cut from different sections and orientations of a sheet of 2024. The grain pattern for the ribs will be different. No matter how hard you try there will be variation in the construction of the ribs. The spar also has some variation during the bending process.

If the ribs are left full size, then they can be placed at different rib locations. It is possible to optimize the ribs that go on the spar for best fit.
Only after best fit arrangement is established should the material be removed for the capstrips arrangement at that rib location.

Also, I use various standard size lathe bits as tools for setting up cuts to the correct length. The aluminum fence is a calibrated distance from the back of the blade. Various arrangements of lathe bits allow for a rib to be put in the jig and maintain a parallel cut.