The main issue here is should the spouse have a desire to have sex with someone else because their spouse is gravely ill.
Me think you heard too many incorrect views about women sexuality.
Me think your views that women ought to do this are that from a male perspective need to be removed from the equation since you will never know or experience the emotional, mental, or physical makeup of women.
As one who have been a caregiver to two moms, watching them go through the horrors of sickness and disease left me numb and unable to move forward at times.
Lord knows how I cannot imagine my beautiful husband who has taken good care of me being ill.
Sex would be the last thing on my mind. Giving him the best that I got and all I got to give to keep him comfortable and smiling until the end would be my goal.
Do unto the sick spouse as you would want them to do unto you. Treat the sick spouse like you want to be treated.
It's called unselfish love.
"In sickness and in health...". Remember those words, or similar ones?