I was circumcised as a neonatal, as so many baby boomers of my generation here in the USA, so I don't have a frenulum, but that area underneath my glans is my "sweet spot." The rim or corona is just as sensitive as my "frenulear" area as well as the groove running from my piss/cum slit (meatus) to the "sweet spot" on the underside.
I think a lot of guys, especially circumcised ones, are very much into their glans from their earliest years. Many guys like to tease their glans and their frenulum/frenulear area/sweet spot when they masturbate. And their partners enjoy exploring the glans penis as well.