The point was that serious thought was being given to the projects as the 1-11 was a durable enough airframe to be considered for the job.
When the secondhand price of the jet was so low, it made it look possible to fit the Tay and offer it at a fraction of the cost of something comparable. Fuel consumption is also supposedly lower for the Tay than an equivalent Spey. The reality is, as you observe, that it never went anywhere as those airlines want something better and the overall numbers would not make sense to them. There was something similar proposed for classic diesel 9s too.
That Maxwell project was something else again as it related to earlier times when aviation in the third world was still seat-of-the-pants stuff, and the Tu-104 with its Soviet style layout may have been attractive to carriers at less than ideal airports with basic runways.
Anyway God bless the 1-11. It made me a nice few quid over the years.