Considering that we live in easily the most litigious society in the history of mankind, and yet the manufacturer themselves told this gentleman it would be fine.... maybe just maybe there's something to it. Now, I'm not expecting anyone to adopt my viewpoint here, but there's a wealth of information available to those who want to research this, and a simple search does the trick:
https://www.fulton-armory.com/faqs/M14-FAQs/308.htm
It's actually fairly common knowledge these days that modern barrel materials are more than up to the task of dealing with the pressure difference between the two rounds, which is the principle concern given the exact same external dimensions between the two rounds. The consensus among folks who know way more than I do, is that it's fine to run either case in either chamber; so I have no concerns about echoing the manufacturer in saying it'll be fine, with of course the proviso that it's a no-no in older military surplus.
As for being anyone's better, I appreciate the compliment but I'm no better or more authorative than anyone else here, I'm simply repeating what's been conventional wisdom here since pretty much the outset of this forum.