Recently, me and my friend have been having a conversation about how a medieval battle in the first ranks really looked like and we reached two conflicting concepts:

1.) I used this video as a reference: https://www.youtube.com/watch?v=RmaYtNW_wR8&t=294s

Lindybeige explains, how unprobable it is for the two opposing shieldwalls (although ancient warfare, I reckon it applies to all eras) to meet shield-to-shield and push against each other. Instead, I reckon, he proposes that battles were fought with a moderate distance (e.g. 1,5 0,5-1 meter), while the shield isn't used as a shoving tool, but merely as a defense.

To me, this concept comes very plausible. If I put myself in the shoes of a medieval soldier in the first rank and I value my life, I would rather keep this distance to increase my chances of survival, as getting into shield-to-shield contact limits my own defensive and offensive abilities.

2.) My friend, however, proposed a different concept. From his battle re-enactment experience, he explained that shieldwall shoving comes naturally. And that in some instances, the first ranks may not even fight themselves. That in those instances, the fight itself may be fought by the second and third ranks, while the first rank pushes against the opposite shieldwall, completely covered, crouching behind their shields, not to get hit.

There may be some truth to that, I thought, since battles were not always fought with spears, but sometimes also with shorter one-handed weapons (e.g. roman legions).

My problem with this second concept is, that re-enacted battles are not fought with the intent to kill. It's a play, not a battle. A re-enactment soldier knows that getting into close-quarters will not get him killed and thus may do something which a normal person wouldn't do in a life threatening situation. Second point, I cannot imagine pushing into my shield and at the same time trying to (fight, if able, and) fend of the spear-thrusts that are aimed at my face. But what about the soldiers who fight with shorter weapons, then?

Thus my question: What do you think about it? Was shoving the other shieldwall a part of the real medieval combat? Or is it something only someone who's not in a life threatening situation would do?

P.S.: (My bonus question that is related to create a realistic depiction of a battle: Maybe a year ago I was reading through some threads here on reddit that talked about the psychology of medieval battles. Someone here mentioned a book, where it was described that front-line clashes were came in waves. For few minutes, the front lines were fighting and then they retreated few meters back, because the psychological pressure on a soldier's mentality in the front line is too severe. It also said, that among those front-lines usually were these few brave individuals, who were the pillars of morale for the nearby soldiers and their deaths may affect the overall morale. It was them who initiated melees. And that similar phenomenon can be also seen in modern-day rioters when they clash against the police. However, I cannot seem to find this thread and so I was wondering, if it sounds familiar to anyone reading this.)