Just as interesting about the Holiday starting question is what it apparently reveals about the other players on the roster.
First of all, it confirms that they are concerned about what we all know is obvious: Jaylen needs to be further moved off the ball. He should be used as a finisher primarily, even when Tatum is out. That means that somebody else in the non-Tatum minutes needs to be the primary ballhandler/initiator. We're not going to see as much of Jaylen dancing on the perimeter "creating" as part of that unit's attack.
The second interesting question is, if they feel Holiday is that person, what does that mean about their feelings on White and Pritchard? White was going to be their starting guard until Holiday unexpectedly became available and he's the easiest personality-wise to accept a bench role (it appears that Horford is very proud about being a starter). Pritchard is having a hot preseason and just got an extension, leading some to believe he'd have a similar role to some extent in the regular season off the bench. This would put doubt on that idea, since Holiday being the primary ballhandler would make Pritchard more of a spacer/off ball movement shooter.
Anyway, all the reasoning seems sound and yes, having the best lineups out there at all times make sense analytically. The Celtics braintrust also obviously has a lot of reverence for the Spurs and you could point to Ginobili moving to the bench as a positive example of this. All that being said, I still think that perception has value and that fans are going to want Holiday announced with the starters, being considered for the All-Star game/season awards, generating "best starting 5" debates, etc. I think all that stuff still has value. Maybe it would be different if, like Ginobili you had already won a title with Holiday and had a long history with him.