Why should some specific people (employers, recruiters in this case) should have a relevant authority as to pretense what a GitHub is supposed to be for.
If someone's GitHub profile is a mess, mixing experiments, serious work, goofy stuff, etc. as a result of their multiple uses of it (it's a _tool_ per se), that's up to them and it's up to no one to say "well, that doesn't look very professional to me, does it? your worth doesn't look great here".
If you put the link on the CV, sure, you just assume that it may be relevant to your profile.
But that's not necessarily a portfolio per se (something _really_ curated for that purpose, which is something specific). If it says so on the GitHub profile page "Portfolio", so be it.
And the recruiter is perfectly fine looking at it, but only for what it is.
What I'm rather aware of, is the pressure/mandate for everyone in the industry to showcase themselves, while that's not a relevant proxy for their fit to this or any job posting.
Sure there are people in the industry making themselves visible through github, twitter and whatnot, and some of these are also excellent. But that's only a tiny piece of the crowd that's available for hire.
If someone's GitHub profile is a mess, mixing experiments, serious work, goofy stuff, etc. as a result of their multiple uses of it (it's a _tool_ per se), that's up to them and it's up to no one to say "well, that doesn't look very professional to me, does it? your worth doesn't look great here".