As per 45APCKING on another thread, you are correct. That is why I said that the poster "may have"
According to 45APCKING, and he can correct me if I'm mistaken on this, the only true landmark to reference from is the gas port at the 6:00 position on the bottom of the barrel
hey I hear my name(s) LOL
the true measure of barrel index is whether the gas port is at bottom dead center.
now, the Chinese may have designed their barrel with a different zero starting point..... but, the original m14 barrel drawings dictate that ALL barrel machining procedures are based off the gas port as zero.
however, the gas port is kinda a hard spot for most guys to verify indexing from.
so we "assume" that by putting a flash hider that we "know" has been machined properly on the barrel , and then using levelling bars behind rear sight and on flash hider front sight base, we can get a very good alignment of the barrel to "index". this is the accepted method and recommended.
as for the feed ramps being an indicator....... to be honest, during a build, the only attention paid to feed ramps is to make sure the peak between the two ramps is not sharp enough to damage brass or impede chambering. Uncommon on Chinese or used USGI barrels but feed ramp peak sharpness is very common with Krieger and criterion barrels and they will actually puncture brass if not treated/dehorned. I've seen some pro gunsmiths skip this step and owners send me rifles that were problematic...... and a 10 minute job with my stones and Bob's yer Uncle

, but that has nothing to do with index so I digress
to verify an index issue, one must examine flash hider for faults. if faulty, replace, then check index with a properly machined unit.
the method using alignment bars is expertly shown in the M14 stickies by Skullboy.