In your final paragraph, you touch on the number one reason I stated the MLBPA is filing the grievance: the rules on service time allow manipulation, which is done in bad faith in regards to the contract. Without this grievance, and subsequent attention it will receive, the union has no shot at changing the rules in the next CBA.

And as far as having to directly give something up to get what they want in regards to service time, well, that’s not always how contracts are negotiated. But yeah, it’s possible that MLB agrees to make change on this issue in return for something they may really want. The back and forth and trade off just depends on the topic and how set in stone each side is, or how far each side is willing to travel to meet in the middle. It’s possible the MLBPA raises the issue with a new proposal and MLB counters with a slightly different proposal, and they just agree.

What I’m driving at here is just because a (random) non-rostered player may be the most qualified for a position, that doesn’t necessarily mean it’s best for that player’s long term outlook to be rushed to the majors as soon as he’s the marginal better option. (I mean ‘long term outlook’ as a matter of baseball proficiency – with the economics of free agency, there’s less incentive than ever to allow a player to ‘learn/develop at the MLB level’.) A team might go with a lesser option at the major league level to allow the (random) player to continue his development in the lower-pressure environs of the minors.

This is where I feel the Olt injury is germane to Kris Bryant and the grievance. Even if we all agree Bryant may have been called up well before Memorial Day, he happened to come up after exactly nine days due to happenstance (an injury) – the timing of the promotion was due to an unforeseen team need for a third baseman. (If Bryant was promoted May 5th, is it even an issue?)

It may have been more shady if Olt sat for five days after getting hit by the pitch, and only then the team decided “Olt needs to go on the DL”, but Olt played two or three games after being plunked.

(In the big picture, I think it’s fair for the player’s union to want to negotiate a clearer remedy if they feel this is such a large problem. OTOH they collectively bargained the rules that exist now, including the lack of clarity in what appears to be a grievance over ‘good faith’. If the players want an adjustment to this specific issue, they will likely need to make a concession to the owners on some other point.)