F
Floyd Davidson
My theory is that this is a mistake induced by the native language of
the poster, where the same word could be used for both.
I doubt the extent of your English vocabulary.
A quick check in any dictionary should show that "doubt", used
as a transitive verb, means "question", and indeed "question"
will be listed as a synonym and/or as either part of the
definition or in the usage of the word.
Apparently this is less common today than it was historically,
because of the dictionaries that I did look at, newer ones use
it vaguely,
"... to consider questionable ..."
while older dictionaries are more explicit,
"doubt v.t. 1) to be uncertain about; question; feel
distrust of. ..."
This last from a 1968 edition.