I think the point to be made was that if you screw up your browser rending to the point of it being unusable on old devices, that could be just as business critical as the data integrity issue.
Making either of those your line in the sand for what a developer should and shouldn’t know is arbitrary. I don’t know a ‘Scala’ full-stack developer that could do advanced optimisation on React render times, or a ‘React’ developer that knows transaction isolation.
Not knowing either of these does not make you an unworthy developer and unless you have a specific need for these skills it probably does more harm than good expecting everyone to know them.
Making either of those your line in the sand for what a developer should and shouldn’t know is arbitrary. I don’t know a ‘Scala’ full-stack developer that could do advanced optimisation on React render times, or a ‘React’ developer that knows transaction isolation.
Not knowing either of these does not make you an unworthy developer and unless you have a specific need for these skills it probably does more harm than good expecting everyone to know them.