Brew core and cask are older on the Xcode 11.6 stack than the 11.5 stack

Also experiencing this, it seems two taps are not being updated by the brew-install step, specifically homebrew/core and homebrew/cask.

Expected:

Updated 3 taps (homebrew/core, homebrew/cask and wix/brew).

Got:

Updated 1 tap (wix/brew).