Which is going to be so little that it's not going to matter. We're talking about fewer than 10 snaps on the year where he doesn't rush in a passing situation.
It always matters when you're talking about quantity of sacks. If he's not rushing the passer, he can't get sacks. That goes for if he plays linebacker 10 times or 100 times. Any ONE time keeps him from sacking the quarterback.
Furthermore, the context of this issue is his over/under on 16 sacks. Last year, he got 13.5 almost exclusively as an edge rusher.
ANY snaps at linebacker is going to be one fewer as an edge rusher. And that one time NOT going after the quarterback could result in one fewer sack towards his overall total.
If what Parsons says is true that he's going to be utilized in a number of ways, then that's going to cut into his sack total. Hence, my prediction of under 16 sacks for the year.