I thought it was a fairly common practice:
"When faced with major surgery, you may have concerns about the risks of blood transfusions. One way to make it safer is with a preoperative autologous donation (PAD), in which your blood is collected before surgery and given back to you during or after surgery if you should happen to need it."
https://www.verywellhealth.com/blood-donation-before-surgery-2549514#Surgery%20with%20High%20Blood%20Loss
I was told it just goes into the general blood “fund”
From the article...
“Although receiving your own blood may put your mind at ease, preoperative autologous donations are really only considered if there’s a local blood shortage and/or your anticipated blood needs after surgery are high.”