Can’t comment on those guys specifically, but producing great steals and blocks numbers doesn’t necessarily correlate to actually playing good real life defense.
In regard to young guys you see a similar trend pretty often. They enter the league and try and block every single shot, causing them to foul often and be taken out of position on fakes. As their game matures (if it does), often they stop playing as risky of defense and play a better positional game (which doesn’t necessarily translate into steals + blocks.
in regard to steals, often the ability to rack up steals just means you’re willing to take risks and jump lanes. There’s been a bunch of bad/inconsistent defenders (iverson, westbrook) who rack up steals by taking risks too often. While they win the gamble sometimes, often they don’t and find themselves out of position and force their team to scramble in rotation to account for them essentially being out of the play