I wouldn't say that adding a publisher name to a title results in a manifestation access point. It is still a work/expression access point—it is just using the name of the original publisher as an identifying element in naming the work (for lack of any better piece of data). Even if "Historical studies (Macmillan)" gets reprinted by Penguin, the "Macmillan" qualifier is identifying the series as a work, not as a manifestation. The work contained within the Penguin reprints would still be identified by the access point "Historical studies (Macmillan)".
So, the publisher *relationship* pertains to the manifestation. But using that name—or any other manifestation element—in an access point does not automatically turn the access point into a manifestation access point. At least, under RDA. Things were quite different in AACR2, when we were indeed creating manifestation access points (which are coming back to haunt us).
Kevin M. Randall
Principal Serials Cataloger
Northwestern University Libraries
Proudly wearing the sensible shoes since 1978!