Steve, sorry to go against you, but to be fair, it sounds like this one is on you. it seems that if you correctly milled your lumber to the stated 3/4”, especially given your understanding of the seasonal and manufacturing variances, then the bit set would have worked as expected. You didn’t take the QC step that ensured your wood was prepared to the right dimension(s) and the manufacturer has no way to make up for those variables.
The reason for the set to be exactly as stated is that the tip of the bit can and should be matched/registered off the actual face of the workpiece in order to ensure the tongue is centered. With some ambiguous oversized dimension, the operator would have no practical means of centering the bit on the workpiece.
Next time, I suggest you use a dado blade to plough 1/3 of of one face, then flip the piece and take the same 1/3 from the other face, which will automatically center your tongue no matter the actual thickness. Or do the same with a straight router bit, which applies the same process to ploughing the groove, except with a bit that is narrower than the finished groove.
I’ve considered those t & g bit sets myself and decided that there are just too many out of my control variables to put them use.
If you hang on to them, you could set them to one face, run the work piece, and then plane the opposite face until the piece is balanced. Just remember that the depth setting needs to be the same for both sticks of wood BEFORE you start planing.