[R-pkg-devel] Why doesn't R CMD check warn that globalVariables() is undefined/not imported?

'R CMD check' will give a warning that 'speed' is an unknown variable in:

  low_speeds <- function(limit) {
    subset(datasets::cars, speed <= limit)
  }

We can tell 'R CMD check' that 'speed' is a false positive by
declaring it a "global" variable.  This can be done, by:

  low_speeds <- function(limit) {
    subset(datasets::cars, speed <= limit)
  }
  utils::globalVariables("speed")

So, far so good. But, why doesn't 'R CMD check' complain about
'globalVariables' not being defined if we use

  globalVariables("speed")

without utils::* and without having an importFrom("utils",
"globalVariables") in the NAMESPACE?

For what it's worth, if I add a globalVariables() inside a function
definition, e.g.

  low_speeds <- function(limit) {
    globalVariables("speed")
    subset(datasets::cars, speed <= limit)
  }
  globalVariables("speed")

then 'R CMD check' will indeed complain about that inner globalVariables():

$ R --vanilla CMD check teeny_0.1.0.tar.gz
* using log directory ?/home/hb/repositories/teeny.Rcheck?
* using R version 3.6.1 (2019-07-05)
* using platform: x86_64-pc-linux-gnu (64-bit)
[...]
* checking R code for possible problems ... NOTE
low_speeds: no visible global function definition for ?globalVariables?
Undefined global functions or variables:
  globalVariables
Consider adding
  importFrom("utils", "globalVariables")
to your NAMESPACE file.

Is this an oversight in R CMD check, or is it implicit that the
'utils' package is attached when installing and checking packages and
we can use 'utils' objects at the top level of a package?

Thanks,

Henrik