Not sure anyone here has really questioned these assignments. Most of the posts are trying to determine the Phillies' reasoning in some cases. I kind of assume that the professionals know more about these players than we do because they see them every day.
My philosophy is that you put the best prospects at their proper level first. Then you fill in with secondary prospects. And fill holes with roster filler. Guys like Brito and Gamboa are at Lakewood because they are ready, but also because they are top prospects (even if someone like Gamboa could easily put up a sub-600 OPS). A guy like Stobbe, on the other hand, may be ready offensively for Lakwood, but if he is switching to 3B full time may not be ready defensively. A guy like Sandberg is probably on his last shot here. I am guessing his demotion is not because he is not ready for Clearwater. It is that the Phillies like other prospects more than him and they now take priority.
Ortiz is probably a 50-50 decision. Would not be surprised if he is at Lakewood at some point this year. The guy nobody talks about who I almost wish was there is Matos. He is a sleeper prospect IMO and was a year older than most on that GCL squad. He is not a good enough prospect to have pushed the promotion, but I think he has more potential than Juan Luis for instance.
In general the Phillies' decisions appear sound. A pretty good mix of aggressive promotions for the best prospects and making secondary prospects earn it.