Idk what "functional strength" is. I personally don't train for it but have no issues going about my day and moving/carrying heavy things. If I was a couch potato I'd need even less to be "functioning".
A mountain climber might disagree but I've never been hanging off the side of a cliff by my hands and needed to pull myself up 20 times.
I feel like folks will arbitrarily call one thing functional and something else not when in reality strong is strong, and most folks simply aren't.
I don't pay much attention to cardio talk but is there a functional speed sect outchea too?
I also feel like that anecdotal example you gave is disingenuous since grappling incorporates mobility, skill, conditioning, and strength/power.
You might be stronger than those blue/browns or you might have better technique or conditioning. Them getting gassed or struggling isn't an indication that your strength work is superior or optimal.
I know a former college wrestler with "old man skrenf" and phenomenal cardio that gives more experienced BJJ dudes trouble when they roll so that's not surprising to me.
Old buddy would smoke me on the mat or in a 5K but ain't seeing me in the gym or on the platform. Doesn't mean he's weak, it just means I'm stronger.