So in the narrow sense this is a bug, or "unusual feature" in Rcmdr. What John does in R/startup.R [1] is a little unusual as he reimplements parts of R's own package management in his package. Which is his right, and CRAN has no problem with it. So it is conformant to CRAN and Debian policies. I understand that that is still frustrating to you but the simple local answer is to ... just install the missing package.
Cheers, Dirk [1] Viewable at https://github.com/cran/Rcmdr/blob/master/R/startup.R#L50-L60 and the lines below it. -- dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org