Thanks for reading - original author here. For the precise quote you mentioned I came up with somewhat format rules which prevented building a framework (code-wise) for this case study. The "caveat" you mention is just an explanation for the chosen ruleset; I believe I haven't introduced any general-purpose DOM/UI code in the case study and instead only describe patterns (correct me if I'm wrong!). I agree with your view of framework value as I professionally use React on a daily basis and will continue to do so, for similar reasons :)