Every time I see the triangle with a 7 I have a little pang of annoyance

I learned about the triangle from Abersold in the 70's and when I went to Berklee I was told to never use it because it could be interoperated as a circle or dim chord.
This was in the days before Finale so it was a real concern when most of the charts you were reading in school were hand written. Calligraphy was a requirement.

Ma7 and Maj7 were the logical alternatives back then but I always thought the triangle was the most elegant, akin to a mathematical symbol .
However triangle 7 (typed^7) is not at all akin to the logic behind a mathematical symbol. The 7 is meaningless and just fills up space.

I am very curious as to when and how the 7 was added to the triangle ?
Was it started here at iRealb?