In the Yang Xiaojia TJQ, from the lineage of Yang Lu Chan. almost all stances, stepping and pivoting are at shoulder with, with back straight, a "C" curve shoulders and chest, power comes from the earth, transmitted out to the hands and arms by the waist, etc. And elbows and arm pits do not touch the ribs, but are generally held is if there is raw egg under the arm pits. And this widening of stances can disrupt relaxantion, cirularity, softness, not to mention mobility in applications and correct practice of the a TJQ form, whether large, medium or small frame styles.
I am 6'2" and 230 pounds, If I widen the stances, my shirfu will say, "not right", and this widening is not part of this very traditional and rare system. However, gradually training the hips and knees to go lower in these shoulder with stances and stepping is encourage, in several ways. There is the usual principle that the knee should not past the toes in various stances and stepping.
Wider does not necessarly equal and improves rooting. IMHO this widening can disrupt actual rooting and stability.
Perhaps the issue is not widening, but gradually sinking the
tian tien going deeper with the knees and hips, as well relaxation of the torso and upper body. and using the correct input from SunTzu's recent post on this topic. Relaxation and rooting are very related.
James