nobody is saying that there aren't experienced co-pilots around. Of course there are. The arguement is about risk mitigation.
Interesting. To broaden this aspect somewhat; there was a discussion a few months ago about F/O landings in strong testing weather conditions or in NNC. The opinion was firmly divided about PF (F/O) staying PF or Captain taking over. This former was more the case in strong gusty x-winds, for various aesthetic reasons: there were even some advocating PF (F/O) remaining so for engine failure or flap/hydraulic NNC landings. IMHO the captain is expected to take responsibility and mitigate the perceived risk in anything untoward.
In the RTO case, for those who advocate F/O's calling STOP, it is likely, unless it is very well trained, that when the Captain is PF & oblivious to the reason, there might be a hesitation as the WTF question is asked. If this happens close to V1, the stop might occur some knots beyond.
The ability to call STOP might well be relevant if F/O is PF and feels the a/c is not quite right. It would be difficult to conduct a conference with the captain as you hurtle down the ever reducing stopping tarmac. The 'unsafe to fly' part of the RTO/takeoff brief might be more apparent to the F/O (PF) than the non-tactile captain.
A debatable topic and one I've never come across in any of my airlines.
The closest I got to it was an F/O can call Stop, but it was advisory. A STOP from the captain was mandatory and always executed from LHS. There are airlines, I believe (BA???????), where the F/O (PF) can execute the RTO from RHS. Is that correct?