To an extent but I reckon Hardwick more than most, which is probably reflective of his personality and values around loyalty.
There's guys like Castagna he will stick with until it becomes a public humiliation and then other guys are dropped before they run out.
I think you are probably right regarding Hardwick and his unswerving loyalty to his favourite players. But I don't see it as a weakness, I think it might even be a strength.
The bottom line will always be that he won three flags with a list that on paper was probably not even top 4 in the league. If he asks his guys to believe in his vision, then he has to believe in them. And I don't think his loyalty to his players has come at that great a cost in terms of developing younger players. Indeed I think his time as coach, since 2017 anyway, has been marked with a small but continuous stream of opportunity for players who want it enough.
Since 2017 we are a champion team, not a team of champions.
For reference, I would encourage people to look at what Jim Valvano did with North Carolina State in 1983. There is a really good doco on it called Survive and Advance. But it really only tells about 70% of the story. You need to read some of the excellent books about what he did that season. It was based around loyalty to what he had and really believing in those guys.
And for mine, I think this North Carolina State's 1983 season has to be the most improbable outcome in the history of sport. Big statement but like I said, if you aren't familiar with the story, check it out.