Why is a single armlock common in depictions of pankration but not in modern MMA?

Question

The sport pankration in the ancient Greek Olympics is similar to today's mixed martial arts in that it restricted only a few particularly damaging attacks so that competitors will use a mix of stand-up, wrestling, and groundfighting. But something I've noticed in many depictions of pankration is the use of single arm locks (attacking shoulder or elbow) after taking someone's back. It just seems unusual to me because in MMA, back takes usually end up in rear naked chokes, which seems like a much more stable option.

Was this actually a common offense in pankration, or was it just artistic cherrypicking? If it was common, why do we see it in ancient pankration but not modern MMA (e.g. ruleset)?

Pancrastinae, a Roman sculpure based on a lost Greek original. It depicts a fighter taking the back of an opponent on 1 hand and knees and using his left hand to hyperextend his opponent's right arm. It's hard to see from this angle, but his left leg is hooked around his opponents' to prevent him from easily turning and relieving the pressure on his shoulder.

Answer 1

There could be a number of reasons for this:

1. Source confusion - The Greeks did also contest wrestling (to a fall) as a separate sport in the same way they did boxing. It may be that the number of depictions of pankration are therefore lower than expected with some being depictions of wrestling and therefore not showing strangles (for example, if we had 10 depictions, 2 showing strangles, and assumed they were all pankration, we'd think strangles were under represented - this view changes if we then find out 5 of the statues are of wrestling as an individual sport attempting to depict throws rather than submissions).

2. Ruleset - According to Miller, (n.d.) the ruleset of Greek wrestling counted any contact of the back with the ground even while fighting on the ground constituted a fall, which makes head/neck control from the rear dangerous.

3. Artistic reasons - It is conceivable that sculpting a wrestler taking a grip about an arm or shoulder is easier than sculpting one taking a choke, and in the case of painted depictions makes the action clearer and conveys the goals better, and this has therefore influenced the artists.

It's important to note the majority of artistic impressions of wrestling/pankration are that - art. They're not supposed to be educational or training resources, and so artistic reasons will take precedence over practical ones when decisions are made.

Choking/Strangling techniques are absolutely present from the historical record in pankration/Greek wrestling, and I would suggest it is probably due to reason 3 above that we don't see them as frequently in artistic representations.