You are misunderstanding the argument and context of the argument while also putting words in my mouth. This, because you still have not watched the video. You are, however, riddled with misunderstandings.
https://www.strongerbyscience.com/size-vs-strength/
Sometimes, people with less muscle lift way more than people with more muscle. Some people gain proportionately more strength in response to training, while others gain proportionately more muscle, even on identical training programs.
On the individual level, you gain way more strength than muscle mass across a training career because strength generally increases faster than muscle mass.
Over the course of a training career, you gain more strength than muscle mass because there are a multitude of factors that can contribute to strength increases on top of increases in muscle mass, so it’s only logical that your strength gains will outstrip your muscle gains.
Hypertrophy’s direct contribution to strength likely increases with training experience, as adaptations that occur very rapidly (such as skill acquisition and changes in NMF) play progressively smaller roles in strength gains. Since strength is highly specific, you’ll likely gain strength faster by training heavier versus training lighter, though you’ll likely build muscle at roughly the same rate regardless of training load (assuming volume is matched).
Hence, building muscle will probably make you stronger, but it will certainly increase your potential strength. A version of you with more muscle will have the potential to lift more than a version of you with less muscle, though you very well may be able to out-lift someone with way more muscle than you have, and you may still be put to shame by someone who’s way less muscular than you.
If your goal is to maximize your long-term strength gains, you should aim to build as much muscle as you can along the way.
Muscle mass certainly influences strength, but it’s also certainly not THE determinant of strength between individuals, and hypertrophy is not the only factor influencing strength gains. There’s massive variation between people in factors that directly influence strength, such as NMF and muscle moment arm lengths. Furthermore, with training, some people gain strength much faster than others, independent of hypertrophy, due to the variable changes in NMF and the variation in ability to learn and master exercises.
Gaining muscle increases one’s potential to gain strength.
Tl;DR
A ton of factors influence strength beyond muscle size and skill with the movements used to test strength. The strength of individual muscle fibers, normalized muscle force, muscle moment arms, and body proportions can all have significant, independent effects on strength.
Just as there’s massive variability in muscle growth – some people gaining a ton of muscle in response to training, and other people gaining very little – there’s massive variability in strength gains as well. Normalized muscle force (how strong a muscle is relative to how large it is) can increase up to 39% for some people and decrease by as much as 5% for others, in response to the exact same training program.
Early on in training, there’s a very weak relationship between gains in muscle and gains in strength. Gains in muscle mass may explain as little as 2% of the variation in strength gains for new lifters.
For more experienced lifters, gains in muscle mass may explain up to 65%+ of the variability in strength gains, highlighting hypertrophy as a key factor for strength gains in trained lifters.
Training style has a big impact on the ratio of strength you gain relative to size, with heavier training generally producing larger gains in strength.