No, not really. That was a digression from the topic of discussion and was really not relevant.
As a sub, it is very likely that Bell played more than just a single position. Some of the top-tier subs as discussed above may have played exclusively one position (for instance when Montreal used Jack McDonald and Louis Berlinguette at LW), but most of the second-tier subs probably played whatever position was needed.
But then look at the 23/24 Canadiens, Bell's last team. Their starters were Morenz, Joliat and Billy Boucher. This was Morenz's rookie season, and he was being broken in, evidenced by his point totals being significantly lower than Joliat's or Boucher's. Thus we have Odie Cleghorn as the leading sub, the only forward sub who had significant ice time (6 points in 22 games to Morenz's 16 in 24); ie, a first-tier sub as I described above. The rest of the forward subs were second-tier, combining for 50 games played, zero points and one minor penalty.
The team used 3 forward subs per game. They already had two players sharing centre. One of the other subs was Joe Malone. Another was Bobby Boucher, whose position is usually listed as centre. There just wasn't any room for Bell to be playing at centre as well. It seems most likely that Malone and Billy Cameron (the only two LHS subs) primarily subbed Joliat, while Bell and Bobby Boucher primarily subbed Billy Boucher. Each of these subs only played a partial season with the Habs.
And it's quite likely that wing subs in the NHL at the time played centre in senior leagues, since generally speaking the best players will play centre (as I indicated in the other thread). But the topic in this thread is leading NHL defensive centres. Having played centre at some point in the past does not make you a centre in the NHL, and occasionally playing it as a sub (while mostly playing wing) also does not make you a centre in the NHL.