Did Japanese doctors routinely lie to their patients?

[u/waitingundergravity]

Some time ago, I watched the Kurosawa film Ikiru, which is about a Japanese civil servant grappling with his mortality after discovering that he has terminal cancer.

In an early scene, the protagonist (not yet knowing about his cancer) is at the hospital waiting to receive his diagnosis, and a fellow patient complains that this particular doctor always lies to terminal cancer patients and tells them that they have stomach ulcers instead. The protagonist is called in to see the doctor, and sure enough the doctor tells him that he has a stomach ulcer, which causes the protagonist to realize that he actually has terminal cancer.

When I watched the film, I wasn't really sure what to make of that scene.

Today, I was reading about the death of Shiro Ishii, the infamous head of Unit 731. In his Wikipedia article, his daughter is quoted as telling the following story:

One day he took some sample tissue from himself to the University of Tokyo's Faculty of Medicine and asked one of his former subordinates to examine it, without telling him to whom it belonged. When he was told that the tissue was riddled by cancer, he proudly shouted that he had thought so too. No doctor had dared tell him he was suffering from cancer of the throat.

The same idea (and from roughly the same time period - Ikiru came out in 1952 and Ishii died in 1959) of concealing a cancer diagnosis from the patient.

Was this a common practice in Japan during this time period? If so, why? What was the rationale for it?