"All of this begs the requisition if yrn=YO and yfwd=yo then why use 2 different <expletive> instructions to say the same thing?"
My best guesses:
Patterns are written according the custom of the country they are written in
Patterns are written by people from different generations and terminology changes
Old patterns get updated and terminology from yesteryear gets mixed with terminology for the time the pattern was updated, which may or may not have happened this decade or this century
Patterns are written by people and people do things their own way
In addition to differences by country and maybe continent, there are probably regional differences as well....much as in Stephen King books he talks about a breakdown lane which I think is called a shoulder here.
Go figure. Patterns written by real people in a real world are imperfect and sometimes rather unclear.
Yes, it makes me grumpy!