I don't think UEFA have got that far in terms of how violent a shirt tug can be. I can't remember anyone getting sent off for a shirt tug that wasn't a goalscoring opportunity. I don't think the ref can be blamed for giving a yellow there.Long story short: yes, if they meet the test for violent conduct, but no if they do not.
The implementation of VAR was certainly better than it has been in the Premier League this season. I know people who've sworn off watching any live football now, because they don't know when their emotions and reactions are real any more!
Not so much. They certainly get upgraded quite regularly, as the organic parts find new ways to skirt them, but they don't seem to have any major gaps to my knowledge.
Now... I can't actually find that as a written rule. IFAB Law 12 only mentions arm/face contact once, and it's under "violent conduct":
How that's interpreted by a governing body, and how it instructs its referees to call it, is a different matter - and I think that's actually what you're talking about here with inconsistencies.
It may be that UEFA mandates across Europe, or even a body below that like IFA/FA within its nation, that the straight arm isn't a red, because it dictates that a straight arm uses negligible force compared to an elbow, therefore it's not violent conduct. I don't know, and I can't say for sure, but IFAB doesn't actually lay that down in the laws of the game. It's an interpretation of that from the law, which fits the law but which isn't specifically noted and which may differ between nations or confederations.
This also applies to the "last man" thing we've seen in this thread. It's an extremely common rule - if the defender is the last man and hoiks the opposing player down, it's a red - but it's not actually a law. IFAB only decrees that the "number and position of defenders" is taken into account; confederations and national associations almost always interpret that as last man = red.
That's actually why we hear a lot of the time of teams and players "getting away with" stuff in Europe they wouldn't in the PL (or vice versa). Both operate under IFAB's laws, but the PL is governed by the FA's interpretation of it and ECL/EL by UEFA's interpretation.
In this case it'd be UEFA's interpretation of the IFAB law, and direction to its referees - and referees aren't perfect at implementing the interpretation. All we can say is the referee, or assistant referee who was literally right there, or anyone else who reviewed it (did it go to VAR? I don't know) didn't believe so, and that's that.
Personally, I regard a shirt pull as extremely dangerous, because - even though it's brief - it can kill, in the wrong conditions, though thankfully a loss of consciousness is more common. Basically a sudden neck trauma which constricts the carotid sinus (where you put your fingers to take your neck pulse) leads to instant syncope; it's actually sometimes taught as a self-defence technique, where you slap the attacker on both sides with the edge of your hands. In some cases, particularly those with undiagnosed cardiac function issues (such as footballers Fabrice Muamba and Abdelhak Nouri, and possibly Christian Eriksen, though I'm not aware of anything coming from that just yet), combined with a high heart rate (such as during a football match), it can cause instant death, known as CiRCA.
Of course it's very rare (I am familiar with a single case in real life, and it was a youngster; Edit: two, both kids, with LongQT as an underlying for the other one), but very much a real thing - usually it's just deeply unpleasant, as anyone who's ever been yanked back by the collar will tell you! - but part of why I'd regard any deliberate action against the neck (and head) as over the line.
I fully appreciate people might not agree, and it does come down to how one interprets that line between what is violent conduct (endangering a player through a deliberate act) and what is foul play (disregarding player safety while acting).
I'm interested in what you think about the Portugal game offside since it's another instance where we see the rules differently.