I know it seems hard to believe and the focus has been on other parts of the euthanasia program
however when I visited a museum in Trier they had a detailed breakdown of who lost their lives at the hands of Hitler’s henchmen gratis the program.
they were very clear that many customers lost their life’s solely because they were old and regarded as a burden to society.
this is an article about it
https://www.britannica.com/event/T4-Program
in essence the program sought to rid society of anyone who was regarded as defective. Old people unable to look after themselves fully or in some way incapacitated through age fell into that category.
It’s possible that different regions interpreted that guideline differently but it was an unpleasant additional insight.