This is an aikido technique that has its roots in jujutsu. Aikido comes from a synthisis of many different styles of jutsu, both armed and unarmed. As a result, you will find some form of weapons training and familiarization in most aikido dojo.
Just like any instance of combat with an armed opponent, these sword techniques would never be easy to execute on the battlefield. The samurai were still taught these skills to give them a small chance of success should they lose their weapon, or some other factor were to present itself to allow them that fighting chance.
In reality, however, the chances for success in a situation like this would have been very slim, but not altogether impossible.
Still, in aikido, we practice, train, and study these movements on both sides. That is to say we study the movements of the attacker (uke, teki, uchidachi) and the movements of the defender (nage, ware, shidachi).
Theirs was a culture rising from war. From the very beginings they served their employer or daimyo in protecting cities. This was before they rose up to power as a class, or in politics. They were servants bred in warfare and combat.
They were experts in warfare and trained for the battlefield. They were experts with weapons such as the bow, spear and sword, and experts in unarmed combat.
They trained constantly in the use of these weapons, for the purpose of combat.
Theirs was a culture of service in war and peace. They were fierce, and for the majority of them, loyal warriors.
Those that survived the many major battles throughout Japan’s barbaric history, walked, limped or crawled away from battlefields. where tens of thousands on both sides lay dead, and another tens of thousands on both sides lay screaming or in shock waiting to die from their wounds.
It was not until around the 10th century that samurai grew into a ruling class in Japan.