From the Conclusions:
"If it is accepted that ‘the designation of subspecies on the basis of arbitrary divisions of clinal character variation is not warranted by today’s standards’ (James 2010), and if that same standard applies to the designation of species, then analyses that are used to assess taxonomic limits should be equally independent of clinal variation. Furthermore, if many modern assessments of taxonomic limits do not adequately account for clinal variation, then it seems very likely that older assessments, from which we inherit the great majority of the taxonomic names and concepts currently in use, were even less stringent in this regard. The aim of this note is to remind readers of the prevalence of multiple, intercorrelated intraspecific patterns in nature, some of them first recognized well over a century ago, and to highlight some of the problems that might arise, and the opportunities that may be lost, if these are not quantitatively assessed." (My underlining)
It appears that much re-evaluation of earlier work could be called for.
The paper is tightly argued and would require someone with much more professional knowledge than I have to summarise it.
MJB
James, FC. 2010. Avian subspecies: Introduction. Ornithol. Monogr. 67: 1–5.