Yes I have, and the doors and corridors of Exo III are remarkably similar architecture to those of Altair IV."
It is true that Dr. Morbius says:
"No record of their physical nature has survived. Except perhaps in the formof this charactistic arch. I suggest you consider it in comparison... to one of our functionally designed human doorways."
https://www.scripts.com/script.php?id=forbidden_planet_8419&p=15
But there are other hints.
In the Krell laboratory he describes the Krell "pastic educator".
"As far as I can make out, they ued it to conditon and test their young....in much the same way we employed finger-painting among our children. I often play with it myself for relatxation. Although working here, I sometimes wish I had been blessed with multiple arms and legs. Now you can see that this headset was designed....for something much bulkier than my human cranium."
So those words indicate that the Krell probably had more arms and legs than humans do, and much larger heads. Thus they probably didn't look very much like Ruk.
Who said that Ruk was designed to resemble an "Old One"?"
So if the "Old Ones" were Krell colonists on Exo III, they might make their robots and androids look different from them, perhaps because it would feel wrong to order around beings who looked like Krell.
But why would they make their androids look like humans? I note that the android making machine seems designed to make androids shaped a lot more like humans than like the Krell probably looked.
Talking to Adams and Ostrow in his study, Morbius says that the Krell explored other star systems and brought back animals from Earth, an unspecified period before their final disaster. Perhaps the Krell only made one voyage to Earth, perhaps they visited Earth periodically.
And Morbius says that the final disaster of the Krell (however long it might have been after their latest expedition to Earth) was 2,000 centuries earlier than their meeting, and thus approximately in 198,000 BC, give or take a few thousnd or a few tens of thousands of years.
So possibly the Krell brought back from Earth to Altair IV specimens of one or more species in the genus
Homo. The species
Homo sapiens is believed to have evolved about 300,000 years ago, so was available to transport to Altair IV for about 100,000 yers before the final disaster. Since Ruk looked a lot like a
Homo sapiens, the Krell may have brought specimens of
Homo sapiens to Altair IV. Possibly the Krell might have brought specimens of a closely related species such as
Homo Heidelbergensis or
Homo rhodesiensis.
The Krell might have used genetic engineering to modify the humans on Altair IV, making them more advanced physically and mentally. And presumably they would have taught them civilization.
And presumably the Krell settlers on Exo III would have brought some humans from Altair IV along.
And if they were as noble as the Krell back on Altair IV they wouldn't have used the humans as slaves. But maybe they were revolting aginst the benevolence of Altair IV and used their humans as slaves. And maybe those humans eventually revolted and were exterminated. Then the Kellon eXo III might have made android slaves who looked like the former humans slaves, to continue with business as usual, until those android slaves also revolted.
Or maybe the Kell on Exo III were as benevolent as the ones on Altair IV and treated the humans more or less as equals. And those humans may have built andorid slaves who looked like themselves, for thier own uses and the use of the Krell, until those android slaves revolted and exterminated the humans and Krell on Exo III.
Wiki says, "The Krell were originally frog-like in nature with two long legs and a big tail. They were never shown, but it was indicated in the original screenplay that the ramps between the steps were designed to accommodate their dragging tail."
So you can agree that the Krell probably didn't look like Ruk and would not not make androids that looked like Ruk if they wanted the androids to look like Krell. So you need to come up with a theory why the Krell on Exo II would want androids who looked like humans, theories rather similar to the one I suggested above.