I think you are the one I have already gone back and forth with this on quite a bit. I remember being accused of adhering to some outdated interpretation of what typical size for a player should be and then essentially having a debate devolve into an argument about arguing. So, i won't do that again.
I will say, whether you agree with it or not, smaller players have a harder time getting off blocks. Arm length has a great deal to do with that ability and smaller players generally have shorter arms. That is not some stone age evaluation, that's a fact. It's the same reason linemen on both sides have their arms measured and why that factors in so heavily.
Also, you can say that the model for a middle linebacker is outdated and provide examples of why, but it is exceedingly easy to pick out examples for why a certain body archetype is still valid.
All of this is why, when debating Myles Jack value it boils down to his physical ability in every single evaluation. No one, in any evaluation I have read or seen, has pointed out any single characteristic of a linebacker as his strong suit. It always comes down to, "this guys has the physical tools to be a tremendous linebacker." I am ok with that evaluation and projection, as long as it's not used to invalidate other arguments based on actual human data and metrics for the position. Facts are he doesn't have great stats or much experience. Those are facts.
I respect your opinion and if you think the model of what a middle linebacker should be is outdated, that is absolutely fine with me. However, don't use that as your means for devaluing someone else's argument. It's an opinion, not a fact.