Multitenant: Resource Manager runs too many sessions

I have posted about Multitenant once, twice, or maybe a few more times so tonight the My Oracle Support post "Excessive throttling by CPU Manager" from article ID 1590014.1 caught my eye for multiple reasons: this is the first time I remember seeing Multitenant on anything other than 12c, and it really surprises me that a simple problem like this creeps up with just a few PDBs after just a couple of minutes!