He flat-out called him the 7th defenseman.
That isn't exactly implying that the competitiveness and attention getting that Hitchcock is praising him for makes him indispensable to his lineup.
Obviously he's the 7th defenseman. That's a given since he was just called up from the minors. But at the same time, the Blues did not just call him up to sit him in the press box all the time. He'll see some action.
Nobody is saying the lineup absolutely needs him. But Hitchcock also flat out said the Blues need competitiveness and somebody to get the other team's attention.
The other team's attention.
I don't think other teams are going to be caring much about him and Ian Cole battling for the #6 spot in practice. Clearly Hitchcock means on the ice and that competitiveness/attention-getting infers to what we know Lindbohm brings to the table that most of the other defensemen on this team, while more talented, don't.