The example you gave me was someone who could only grapple 123 days a year if they litterally go everyday 3 days a week, no injury's breaks ect as opposed to 80- 100 days if you include strength and conditioning and it's supposed to take "forever" to get to black belt.
In the end the difference in experience will only take a 1-2 years to make up vs completely behind on strength, the difference plays out in the long run.
And yes if you rotate your training you can see gains from only strength training 1x a week, those will act as active recovery weeks, which is actually really good for strength.
Then lift 2x next week, it's the same as lifting 3x a week you're just stretching out the rest days, as long as your going heavier or getting more reps with your working set you're getting stronger.
And you should be doing body weight work and plyo before class regardless, you're completely undermining strength and conditioning even comparing that little 15 min bodyweight warm up too a full training day dedicated too lifting.
Wait a second: 3 times a week x 52 weeks a year = 123?
It's actually 156... And in your scenario the lifting guy trains 6x in 3 weeks so 2x a week on average = 104x per year.
I'll spare you any more math. The guy who only grapples trains 50% more than the other guy.
In 5 years, the guy doing just grappling has 780 classes while the other guy has 520.
In those 5 years, he has 260 more classes - that's the equivalent of 2.5 years of training for the guy that's lifting. That's an extra 390 hours of mat time!
Let me reemphasize so the point is lost - it will take 7.5 years of training for the guy lifting weights to have the same amount of mat time as the guy only grappling has in 5 years, under these assumptions.
In 15 years of training grappling only guy will have 7.5 years more training years relative to the lifting guy's years of training. So it will take him 22.5 years of training to get the same number of mat hours as the guy who just grapples!
This doesn't even take into account that it's virtually impossible to progress well training twice a week once you are no longer an absolute beginner.
Anyway, lifting is great. Have at it. But don't make it seem that somehow lifting will be more significant for progression than grappling.
Certainly, each additional hour of mat time per week after a certain point adds less marginal value compared to the hour before (diminishing returns), and at some point lifting or cardio or outside work becomes more valuable to your progression. The dispute here is where that line is drawn.
Personally I would say very conservatively that anything less than 8 hours per week and you are better off just grappling. The slope of the progression curve for someone training twice a week vs three times vs four times is tremendously different. In my experience, it only starts to come back down (in terms of the rate of increase) between four and five times, and then five and six again.
Basically, unless you can train 4x per week and lift, if your primary goal is to learn how to grapple, spend all your time grappling. If you have more time, then consider adding lifting at that point.