It's rare that any of these components exist on their own as independent arts- generally, if you find someone who teaches 'kenjutsu', they're usually fraudsters teaching their own idea of what they think Japanese swordsmanship should be. You will find many that focus on kenjutsu, but in most cases those schools do still include a few other components. Over time, many ryuha became more specialized, dropping components of the curriculum that were no longer seen as useful. Anything the headmaster would think it would be useful to pass down. They also included all sorts of esoterica and lore. You might see a combination of the following- kenjutsu, iaijutsu, sojutsu (spear), kyujutsu (archery), naginatajutsu, shurikenjutsu, bojutsu, jojutsu, jujutsu, knot-tying, swimming, ettiquette, field-fortification and so on. A ryuha's curriculum is typically composed of many components. Pre-modern Japanese martial arts, koryu bujutsu, were organized into schools or academies called ryuha. We need to clear up what you mean by 'sword forms'. I think your question is predicated on a certain misunderstanding about how Japanese martial arts are organized, which is understandable because it's incredibly confusing and has changed over time. And some styles begin their "katas"/"forms" with a symbolic drawing of the sword before you go into guard. Some of us do practice with scabbards and belts on, although few. It is kind of pointless, it is more for style than it is for in-combat function as the act of sheathing would suggest it is over. On the point of sheathing, I think this is the most obvious one why it wasn't really written down or big part of other arts. And if I am going to be a bit bold, I would say that Iaido/Iaijutsu is the outlier and oddity as only the Japanese seem to have gone so into the drawing of the weapon, what circumstances or principles that lead to this I do not know.Ī couple more pictures of guard positions that might suggest being sheathed or followed directly after drawing. There are plenty of sources on grappling and dagger play that I would say support this to some degree. Should someone attack you out of nowhere you would perhaps draw the sword with a strike and back off while in HEMA, I personally feel like the go to action in such a situation would be to pull your dagger, go in, and grapple. One reason I think that there isn't much unsheathing techniques in HEMA, and many other weapon arts as well might very much be with their approach to dealing with such a situation. Some later sources talk about drawing the rapier as well. And some sources telling us this under-arm guard also symbolizes having the sword sheathed.
There exists drawing and sword drawing techniques in HEMA, but they are few and sometimes not directly stated, a not too uncommon starting position for one-handed sword, especially with the buckler(small shield) is with the sword under the other arm. So I will do my best to try and explain MY thoughts on this.