smichr/sympy — comment on commit 0dca3dc37ae873b1ebfd3cc2a32c7694727beccc
File: sympy/simplify/simplify.py line 963
By smichr:

So the calling program can get the args back in canonical order for processing. My first pull request had list handling; this pull request tries to build off of what was already present and uses match on the expression. And for that I need an expression in canonical order. Anyone else using this wouldn't have to use that flag.