Ovy's fan here. Ovy is not on the same level defensively as Crosby yet Crosby has always been overrated defensive player period. It is a joke that some claimed that he should have serious Selke consideration in some seasons.
Sums it up well how I've always thought about Crosby's defense in general and compared to Ovechkin.
His defense becoming overrated really took off when he was no longer competing for scoring titles, as some media and fans were desperate to keep him in the conversation for the NHL's best player. This led to his 2016 Conn Smythe being essentially a lifetime achievement award.
In the context of this thread, I don't think anyone tried to argue he was on the level of Kopitar, Bergeron, or Toews defensively. It's more that they thought his defense was good enough to close the gap between him and McDavid after Connor became the annual Art Ross favorite and Sid was hardly a contender anymore.
To be fair to Crosby though, there is some important context with regards to his ES GA/60. The Pens as a team usually haven't been as good defensively as the Bruins, Hawks and Kings. Not only due to MAF being an inconsistent goalie, but also with the Pens not having a d-man on the level of Chara, Keith, or Doughty. This was the reasoning I gave in a thread for why I thought the Hawks and Bolts rank above the Pens for multi cup winners in the last 10 years.
Also fair pointing out that his defensive metrics still look better than Ovechkin despite Ovy playing 4 seasons for Trotz this past decade. And I'm a bigger fan of Ovy than Sid.