When I have worn entirely non-Masonic aprons to do carpentry or stonework, I wore it outside everything else--could that be the reason the practice for the Masoninc apron is to wear it outside the coat?
And herein lies the problem: It's not a universal Masonic practice. Similar to apron designs and dimensions, the rule of coat over or under the apron varies region to region. I also have a picture of my Lodge's founding officers in 1942. Several brothers wore their single breasted coat over the apron (unbuttoned), while those in double breasted suits wore the apron over. One of the older brothers said that the rule might have changed in the 40's or 50's, but I would need to see a master copy of the Grand Lodge Law from each year to verify.
But more often than not, I hear "that's how we do it in Texas," as if that's a good enough reason, disregarding the fact that we owe our masonic pedigree to Louisiana, South Carolina, and Pennsylvania, each of which practice far different esoteric work and manners than we do here.
And if the law really did change, then my answer to "that's how we do it in Texas," will be "today, but not always."