Yes both of those combinations could have been ordered. Even in 1970 allot (maybe most) cars were still ordered and buyers would wait for the car to be built and shipped to them months later. Did add to the excitement and anticipation. There were recommended combinations Ford would use to build cars meant for floor stock based on their research and records.
Also when you compare those combinations (like options) where few were made remember this basically means that those were unpopular and few wanted cars built like that.
The information was published in many period items, for example in the 1968 Salesemans Facts book. There were separate pages for two tone and non two tone cars. In 1969 and 1970 there would be separate pages for those two and for Eliminator.
I have one of those 1970 dealer binders with all the little swatches of material in it. It’s one of my favorite pieces of memorabilia. I love looking through it and imagining how I’ll order the Cougars I’ll buy when my time machine finally works.
The books were primarily for recommended combinations. I think that you could order any combination you wanted provided you put down an acceptable deposit. As to 1968 paint code “B” according to Kevin Marti’s Cougars by the Numbers, there was one standard with interior code “UB” which would be a parchment interior with blue components.