The proposal for the WTB never went anywhere because it was completely unrealistic and the developer, more like some crackpot visionary from Italy, didn't even do a feasibility study as the city requested.
I have a newspapers.com account so maybe I'll do some fun research about it and the Landmark Capital Tower which was I believe Phoenix's 2nd-tallest proposal--also, feel free and DM me or post something interesting if you want me to look up something about it as I have access to the archives of the Phoenix Gazette and the Republic and some other old stuff.
Anyways, midtown exists because it was free of the grime and squalor of downtown that had been creeping for a while, even long before WW2 with the advent of streetcar suburbs. After WW2, Central Avenue was already the city's signature boulevard with high land values (it had a lot of mansions and estates prior to towers) and the development of Park Central signaled the death knell for downtown retail until the 1970s.
It was the Central Phoenix Plan of 1971 that did envision unlimited building heights along Central from 3rd to 3rd with a 500' to 250' height limit from 3rds to the 7ths. This is represented by the HR zoning district at
https://phoenix.municipal.codes/ZO/632, but I don't think anyone would be rezoning to that today with PUDs and WUs taking over.
But speaking of zoning, it turns out that the approved Urban Form plan for downtown is causing a LOT of problems with developers as they were collectively filing for a bevy of zoning code text amendments over the last several months of 2020, each of which is the worst incarnation of spot-zoning I've ever seen. Apparently developers are having to go this route instead of the much easier variance process.
https://www.phoenix.gov/pdd/planning...zstaff-reports
I'm curious to see why this hasn't been brought up before. Planning and Council seem to be dropping the ball here.