WSPR itself is not Godfrey's invention, and in fact depends on many radio amateurs, globally, sending, receiving and analyzing signals - for the purpose of measuring the atmosphere's radio transmission parameters, I believe. Godfrey may have originated the claim that it could be used to track aircraft at long ranges, and that claim seems to have been met with considerable skepticism on the grounds of poor signal/noise ratio.
Godfrey claims that his WSPR track matches that from the Inmarsat data, where the latter is available. In evaluating that claim, I would first want to know if the WSPR track was developed without any input from Inmarsat or other sources.
UPDATE:
There is this article [1] on a blind test of the ability to track aircraft. It looks good here, but then I read this:
'There was one error of note, the initial turn of the aircraft after departure was to port and not starboard. Mike commented “I should have told you that aircraft departing NSFA on RWY 08 will always turn to port due to terrain clearance considerations. If you’d known that then no doubt the first part of the route would have been a bit more accurate.”' [my emphasis.]
One should not, of course, be providing additional evidence in a blind test, and the suggestion that this should have been done raises doubts about how the test was conducted: for example, did the person performing the analysis know the general features of the flight, such as its destination? A more convincing blind test, IMHO, would go like this: "In the interval <begin> to <end>, one airplane passed through <some region>. Develop a plot of its flight before and after, as far as possible." - and there should be more than one test, of course, and perhaps they should say, truthfully, at most one airplane...
[1] https://www.mh370search.com/2021/08/29/gdtaaa-blind-test/