A perspective :
Incentives, social proof and momentum are powerful things which might explain why this could still be applied in 2021 (I have no connection to Amazon or know anyone there so this is a theory). What do I mean?
Imagine you are a newbie who just joined a project that has successfully done what Jeff said in the memo. The success of undertaking that would have meant that your colleagues will want to continue doing this (threat of firing or not :) ) and pretty soon you'll get sucked into it and hopefully see the rewards of such design.
Soon, another team notices your team consistently getting things right and getting rewards so they have an incentive to follow (social proof). This becomes department wide next and so on. This is where momentum comes into picture. It is 2015 (let's say) and there are a dozen new departments. All of them reasonably want to get going quickly so they take up patterns that worked for other in the org. 6 more years pass by with more successes and there's no real incentive (at-least org-wide) to do something different to the one that works. My educated guess: The memo is still followed.
Imagine you are a newbie who just joined a project that has successfully done what Jeff said in the memo. The success of undertaking that would have meant that your colleagues will want to continue doing this (threat of firing or not :) ) and pretty soon you'll get sucked into it and hopefully see the rewards of such design.
Soon, another team notices your team consistently getting things right and getting rewards so they have an incentive to follow (social proof). This becomes department wide next and so on. This is where momentum comes into picture. It is 2015 (let's say) and there are a dozen new departments. All of them reasonably want to get going quickly so they take up patterns that worked for other in the org. 6 more years pass by with more successes and there's no real incentive (at-least org-wide) to do something different to the one that works. My educated guess: The memo is still followed.