Hi - in cross-section, all mitres appears as a V shape , whether cut with a single or double pass of the wheel and really the only way to tell whether made by one or two cuts is by looking at the final tip of the arm - that truly last mm should be a symmetrical true point in a single pass, or whether one of the sides of the mitre is a smidgen longer than the other indicating two cuts.
I will try and add another picture showing the slightly 'off' appearance when there are two passes.
Mitres on quality glass, post middle C19, IMHO would probably be made with a single pass of the wheel - leaves are sometimes cut in two passes, deliberately, or perhaps the glass was presented 'off-centre' to the wheel, to achieve a light and dark appearance. One of the best examples of this two-tone effect, from a mitre, is on the fish motif vase - page 134 - in Hajdamach's '20th Century British Glass' . Kny was another exponent, who when he was working for Stuart made leaves come to life by innovative cutting of the mitre outline.
I'm guessing, but would suggest the mitres your St. Louis bowl were cut with a single pass of the wheel - they were high end makers and a single pass is less prone to visual errors. But, have a look at the tips of the cut (out toward the rim of the foot) - the appearance should tell you which method. Sorry, don't know which leaves you're speaking of