Johann Ernst Galliard (1687-1749), the man who screwed up?

Wikipedia:

'(...) Galliard studied composition under Farinelli, the director of
music at the Court of Hanover, and Abbate Steffani. In addition to his
composition ability, he was also a capable oboe and recorder player.
Galliard made a step forward in his musical career when he performed
one of his original compositions. This Sonata for oboe and two
bassoons debuted at one Farinelli's concerts. Galliard earned an
esteemed seat in the chamber music of George, Prince of Denmark.

'Later, he moved to England where he would become the next
chapel-master of the Somerset-House. Galliard became a familiar face
in high society due to his proximity to and frequenting of the royal
residence. In response to war victories, Galliard composed Te Deum,
Jubilate, and three additional anthems.

'Bigger and better things seemed promising following his participation
in the founding of the Academy of Ancient Music. However, in the scrap
for kingdom wide directorial status, Galliard fell short to greats
such as Handel and Bononcini. He wrote the music to Calypso and
Telemachus upon the request of a friend, the poet John Hughes. Despite
approval from his peers, the show was a failure. As a result, he was
refocused on his oboe performance.

'He joined Handel's Italian Opera in 1713 as an oboe soloist. Galliard
composed several more cantatas to texts by Hughes and Congreve. He
published an opera, music to the Morning Hymn of Adam and Eve taken
form Milton's Paradise Lost, and a large number of pantomimes (...)'

He doesn't *sound* like a bumbling idiot who would write down a
completely wrong theory of the diatonic scale. Good enough for Handel
and the royal house of Hanover - but apparently not good enough for Brad.

Galliard is, actually, only one of many sources in the Baroque and
Classical eras which describe the diatonic scale in terms of major and
minor tones, which usually implies an untempered or Just form. See the
Barbieri article in Early Music.

'... Francesco Galeazzi — who spent many
years in Rome as a violinist at the Teatro Valle — stated in
1791 that the best performers changed the position of the
major and minor tones according to the key of the composition.
He included a fingering chart containing such
alterations, by commas (illus.2). Furthermore, he suggests
that his chart would make
"the less precise players laugh heartily, especially the ordinary
ones who play merely for the practice" ...'

'... Towards the end of the 18th century, the French experimental
physicist Jacques-Alexandre Charles demonstrated —
even at the Paris Conservatory of Music — that
Giambattista Viotti and Pierre Baillot employed a kind
of just intonation in which G-A was made equal to a
major tone (the narrowed 5th in the key of C major was
thus A-E).'

Strangely enough, such JI-based sources were ignored by Barbour and
the stable of temperament fanatics, who followed him in seeing
everything in terms of a set of 12 fixed pitches.

It is very easy to 'prove' something if you focus on the sources that
say what you want to hear and ignore the others, or label them as
'screw-ups'.

By what standards should we consider Galliard a less trustworthy or
significant source than Tosi? (Or Barbour? Or Haynes? Or Lehman?)

Isn't it conceivable or even quite likely that a large fraction of
18th century musicians actually took a JI diatonic scale as their
model, seeing the tempered intervals of the keyboard (if they thought
about them at all) as a peculiar compromise only necessary for that
type of instrument?
~~~T~~~