I have been able to find a copy of G.A. Wainwrights paper here: [archive.org] so updating the discussion relating to Conman's claims:

1. Wainwright cites a secondary source of Dieterich by leveraging select quotes contained in Nock and in doing so has missed the fact that Dieterich had already accepted Meskhetiu to be the Big Dipper and hence instead of supporting his argument, the citation creates a form of circular logic. (Conman p67). Reviewing Wainwright, it appears that this is made in reference to Wainwright's statement (Wainwright p373) "A mystical text of Graeco-Egyptian origin speaks of 'a golden calf's shoulder which is the Great Bear'." which is the only direct reference to Nock and appears to be the key statement Conman is referencing.

2. Wainwright leverages a report by Mariette alleging that “the Beduin” of the Western desert still call the Great Bear er Rigl, ‘the Leg’. According to Conman, Mariette’s claim is not supported by modern evidence.(Conman pp67-68). Wainwright makes this claim on page 375 as a final point of support for the assertion. I am in no position to refute Mariette's claim as Conman does. I would need to check Mariette directly to clarify the connection being made as it could be referring to a different star lore altogether.

3. Wainwrights opinion was based on the fact that in the single image of Meskhetiu he analysed there were seven stars, arranged loosely in a pattern matching the Big Dipper. Conman refutes this by supplying images from nine coffins published by Neugebauer and Parker thereby showing that these coffin images present stars arranged in patterns that differ markedly to the Big Dipper. (pp68-71). Wainwright (pp373-374) says "Although the three stars of the lower part of the Mshtyw in the Herakleopolitan pictures are not quite in place, the group is self-evidently the Great Bear but drawn when standing on end as it does in the eastern skies." Conman has shown that for this proposal, the lower three stars in Wainwright's proposal are entirely out of place unless you perform a horizontal flip or mirror image of the Great Bear / Big Dipper. In presenting the additional coffins where Meskhetiu is drawn consistent with the Herakleopolitan example Wainwright puts forward, a valid question is raised by Conman: if Meskhetiu is a constellation, why would the Egyptians have drawn it so consistently in a form that is never seen in the sky?

Conman has, in my opinion, done enough to call into question the identification of Meskhetiu as the Big Dipper in point 3 above. Points 1 and 2 would add to her argument if they bear out.

References:
Conman, J, Ancient Egyptian Sky Lore, Decan Wisdom Books, 2013
Wainwright, G.A., A Pair of Constellations, Studies Presented to F.L.L. Griffith, Egypt Exploration Society, Oxford University Press, 1932