I don't think so. I don't want to take the time to write out the quote but...
John Hench wrote a book about Disney Design. He suggest the BTMRR DL is inspired by the landscape of Bryce Canyon. The color of Sedona was used in FL to better work with the blue sky there.
If you look at a picture of BTMRR DL and Bryce side by side, you would think the color and rockwork is a clear match. If you look at Sedona and BTMRR WDW, the color is spot on, the rock similar.
I just think that Walt didn't have anything to do with BTMRR in WDW. Not only has he passed before seeing DL's version to make a change for WDW. Nature's Wonderland RR was still in DL for a decade afterward. But also I think his mind was probably well past building newly concieved attractions for DL. He was probably thinking more about Epcot and the wide expanses of WDW.
Only Dave Smith is trustworthy within the Disney company to make worthwile speculation on what Walt though.