I disagree with your 2nd assertion. Even engineers who are less tech lead style engineers, can gain a significant boost in productivity by being able to quickly run through POCs and build an understanding of surrounding areas of their work, so they are able to contribute more.

For eg I am able to make React changes much faster and the changes are higher quality, given frontend dev has never been my job role. I’m able to spin up test harnesses, write throw away glue code, test against large datasets, etc