A reading of
ch6 and
ch8 shows that NACA had both experimented with the all flying tail, and recognised possible pitch control difficulties in the X-1, hence the contract requirement for a trimable stabiliser. When Yeager complained of the dangerous nature of control difficulties in pitch it was no great leap, in my opinion, for Jack Ridely, the X-1 project engineer, to come up with the idea of modifying the stabiliser to "all flying", based on prior NACA flying tail research. Miles can be said to be prescient in their appreciation of the problem in the design of the M. 52, but I don't think they could claim to be the "inventor or originator" of the all flying tail. The US kept the X-1 flying tail, and the fact it solved the supersonic control problems, a secret for 5 years, so Yeager and other sources state. The first application on a production aircraft was the F-86E.
Edited to add I came across this in digging around.
http://www.nasa.gov/centers/dryden/p...main_D-558.pdf If you go to page 69 you will see the M. 52 myth debunked.