Is the 2006 AAEP Proceedings, a paper written by Stephanie Valberg still considered current or even accurage for EPSM horses?

It was offered as a response (by a vet) to the question as to whether EPSM is inherited...
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Although the prevalence of PSSM is 6% of Quarter
Horses in general, it can be as high as 42% on some
breeding farms.22 This suggests that PSSM may
be inherited within particular bloodlines. A familial basis for PSSM has been suggested from pedigree analysis and by limited breeding trials at the University of Minnesota.5,20 Although pedigree analysis initially supported an autosomal recessive
pattern of inheritance, identification of PSSM in
Quarter Horse-crosses indicates that a dominant
mode of inheritance is more likely.6,21,22

She goes on in the paper to write,

No reports on the potential inheritance of PSSM in
Warmbloods have been published.

EPSM and PSSM are considered synonymous for purposes of discussion of the inheritance pattern and prevalence of muscle disorders in a variety of breeds in this particular paper.

At this time the above information is still considered to be accurate though contacting U of Minn may get you more information that hasn't been published yet.