If you have a spanner on the crank and have weight on it so that you are just about to turn the crank against load the front run of camchain will be tight no matter where the cam is.
The very first print of the cb70 manual from Hona for workshops at dealers makes no mention of positioning the crank and just says to loosen the lock nut and bolt then tightening the bolt and lock nut.
It also has a caution in big bold writing
"Do not apply additional pressure on the tensioner push bar"
Yes you did qualify your statement with "as long as..." so you are right. If you are pulling forward, you'd be OK. If one simply selects a crank position without pulling forward, one might be in one of many places where the cam would jump forward.
I remember reading the first manuals, and the method was not ideal. Without the "position", or without applying pressure on the wrench on the cranknut, you're at the mercy of the cam as to whether you'll get a good adjsutment or not. By setting the 15 deg ATDC, you don't have to maintain any pressure, the cam is trying to back up. Makes it easier to get a good adjustment every time.
As to the last caution, I would apply pressure to the adjuster only to make sure the adjuster rod was moving freely. Back the crank up and forward and feel it move. THen let it go to seek its own level via the spring.
You likely know all this and more. I'm writing some for the sake of others.
