It depends on how you define "built-in" exactly. I would argue that in this context, if the end user isn't aware that an external library is used under the hood, it still qualifies as built-in. In which case, R has plot() in its stdlib.
For the aid of the unfamiliar and those unwilling to just google (I often am one of these in other discussions), a number of functions in fortran that operate on array types are built-in to the language and do not require linking in, these are called "intrinsic procedures" in fortran's parlance. They are generally implemented for modern compilers on modern OS'es as libraries of course linked in during runtime like the C stdlib is in C (gfortran's are a C library last I checked although I'm not super knowledgeable about the details there). From the user's perspective, they need not be linked during compilation. External libraries (modules in modern fortran) on the other hand require you to link them in and also have their modules in the compiler's module path, similar to includes but not quite the same as modules are binary files.
Anyway, this is discussion is all for the sake of teaching students. For a python learning student, I assume they do not start from zero and instead told to using anaconda or some build script that gives them a standard jupyter install. From then on in the code they use, matplotlib and numpy appear on equal footing, a set of function calls that just have different prefixes, in their eyes. This surface level similarity is what I mean by them appearing to have convenience level. The fact that jupyter installs are pretty standard and have loads of documentation helps ameliorate potential issues during installation.
In fortran on the other hand, you do not need an external module for the array facilities (things like shape, dot_product, things for initialising arrays, etc) given the built-ins and the first class nature of arrays. However, you will need to `use` a module for plotting (fairly easy, essentially one line for importing) and link it and add it to the module path (potentially fraught). This is what I mean about them appearing on different footing, from a naive student's perspective.
While there are attempts to provide a nice package system for fortran, it's generally the wildwest out there just like it is for c++ and c, so unless the instructor essentially has them work only on lab machines they control, using external libraries seems to me to be a huge source of headaches when dealing with students once they go off to install it themselves.
