Depends on the type of hysterectomy. If it’s a partial where the cervix is not removed, it should not change anything (the vagina and cervix are still in the same place, and there is no geometric change.
On a total hysterectomy (removal of the uterus and cervix (does not include the ovaries)) the usual reports are 1/2” to 1” loss of length (things shorten up where they removed the cervix from the vaginal wall and closed it up.
Some doctors will recommend that women use stents after total hysterectomy to prevent/reduce scaring and to keep the vaginal size that the want.
Hope that helps.
You are saying that a hysterectomy actually shortens vaginal length?