Exactly! The ST to me is the southern tier of states. One time I did it using 90 all the way past New Orleans from FL. Then I went across TX following roads that took me through Odessa and midland, etc etc.
Another crossing went on 19-98 out of FL along the gulf waters. Another followed 20 out of FL between90 and 19-98. Another followed 90 again. In LA I have followed ACA's route, 90, 190, and various roads. Another crossing of TX took me along the gulf to Post Isabel and Brownsville and north along the border road to Van Horn. Another crossing took me into Marfa, etc. On one crossing I went north at the Salton Sea and cycled into Los Angeles instead of San Diego.
I tend to agree the same roads can get boring. We want something new. Highway 90 and the FL pandandle are always pretty good. But getting out of the eastern US tends to be a bit --ho hum I've seen it all thousands of times. When will the scenery start to change? I like the changing scenery to rugged western mountains, cactus, plains, prairies, and gunfights at the OK corral.
ACA's mapped ST is just fine. I often take the interstate across TX, NM, and AZ. It seems more direct. The scenery is comparable. Services are more than adequate. However, road surfaces often are not really good for cycling.
A great many people use interstates which might increase the likelihood of running into some maniac. The FBI have a special team investigating serial killers operating along the interstates. Check it out on google. It's scary. Ladies, I advise you not to cycle the interstates alone, and if you do, it might be a good idea to avoid truck stops. Look at the FBI's map where bodies have been found. Almost all were women, and those are only the ones who have been found. A great many more are missing, and you know that means. They might never be found. There are some extremely nasty characters running around just looking for women to murder. It's a terrible thing but true. I would advise women to avoid the interstates.
I have used interstates alone a number of times through Sentinel, AZ, Tucson, AZ, Yuma and into Winterhaven, CA on the Colorado River. The ST to me means only FL, AL, MS, LA, TX, NM, AZ, and CA. The roads are any roads and the towns any towns.