Yeesh, the capital letters. ;-)
Yes, thinking on this subject has changed considerably since the early 1900's. We are now far more emphatic about getting the patient out of bed (OOB) and moving around after surgery, and that is largely to do with concern about blood clots, but it is also because moving helps with just about all areas of recovery.
Here is a fun little med student mnemonic regarding the causes of fever in post-op days, roughly correlated with the number of days after surgery: the five Ws. Wind, water, wound, walking, wonder drugs. Three of these are definitely helped by getting out of bed.
Wind: the lungs can partially collapse after surgery, causing something called atelectasis. Getting OOB helps expand the lungs.
Water: the urinary system can be affected by both the shock of surgery and by anaesthesia. Urinary retention is bad for you. Also, almost everyone gets a Foley catheter during any surgery involving general anaesthesia, which also can lead to retention as well as offering an entryway for bacteria causing a UTI. Getting OOB helps with this because it helps get everything moving again, and a patient who is OOB is more likely to want to use the bathroom themselves.
Wound: can become infected. This one's not really affected by OOB.
Walking: a DVT (deep vein thrombosis or clot) can form with stasis (sitting or lying still). This is also why they advise you to get up and walk around during long plane trips. Getting OOB, again, helps.
Wonder drugs: you can get a fever from a reaction to the antibiotics. For this, we just have to stop the drugs.
Now aren't you sorry you asked? ;-)
Fourth year medical student.