Bill Tindall
The problem is that a M&T joint needs to be precise to just +/- a few thousandths of an inch to be "right". Hence, it is particularly demanding of any "production" method of achieving it as opposed to hand fitting.

I cut the tenon cheeks as you describe. I have spacer blocks for the tenon jig that match the width of all my mortise chisels and bits. Precisely cutting the tenon thickness is therefore reliable.

I have been using a marking gauge set to the tenon depth to scribe the shoulders in the rail pieces. I cut almost to the scribe line with a band saw and then pare to the scribe line. The paring is fast if the band saw cut is close enough. For a few tenons it may be faster than setting up the table saw for the technique you described. But I will give what you described a try next time.