Altherr and Nola were question marks this offseason, it would have been irresponsible for the FO not to explore veteran alternatives.
Quinn simply hasn't had enough PA, while he's talented, if you watch him hit, he overswings and could use a half to full season at AAA ball.
They owe nothing to Kendrick, they gave up nothing of value to obtain him, and if he doesn't produce he'll be headed to the bench, if he does, he's July trade bait.
Same with Saunders, Hellickson and Buchholtz.
If Altherr keeps hitting, he'll work his way into the lineup, power, speed and great defense is hard to keep on the bench.
I suspect they don't want to rush him, wrist injuries are notorious for taking long to heal 100%, so being conservative the first half of the season is not a bad thing.
The young pitchers will start every five days at Lehigh where they can work on their mechanics and secondary pitches without big league pressure - when they're ready to come up it'll be obvious - not by getting AAA hitters out (Lively did that last year) but HOW they get them out.
My suspicion is this team will look very differently in August than it will in April, and the whole point of this season is really to get the young players ready for 2018.
And in MHO, there are advantages to both players and the team spending more time in AAA ball, players get to work on skills in a low pressure environment where they can focus on skills rather than outcomes (i.e. hang a breaking pitch or signal a changeup and not lose sleep over 450 HRs), which can pay off down the road (it's hard to experiment with a new stance or grip in the majors), while the team doesn't start the clock ticking until the player is developed enough to be a positive WAR player.
The Show is not where a young player should learn his craft, it's where he should practice his craft once learned.