My dad was in the Navy, so we grew up moving every two years.
Whenever possible, my mom had us move over the summer. This sometimes meant that we were staying in the Navy Lodge, other times it meant that a condition of sale on the house was that it wouldn't close until 2 weeks after school was out (a week to pack and get our stuff out), and SOMETIMES it meant that we'd already be living in another state, while the house was on the market.
My first grade year (and I was the oldest) was her trial run an moving in the middle of the school year, and she hated it so much that she refused to do it again, if she had any choice (sometimes she didn't... if orders came in November... she would hold out until winter break, but no longer).
On our side of the street (being parents now, ourselves), my son hated kindergarten.
Don't get me wrong... he had a FANTASTIC teacher (30+ years teaching who was reprimanded more then once the year my son had her... because she had the *audacity* to let the kids who already knew numbers and or math DO those things, and ditto on reading, and ditto on when it came up she taught the kids how to tell time. The new "thing" in the district we were in was "Qualitative Math" until the 2nd grade...aka math with no numbers... and "Equal Reading" aka, no kids were allowed to read anything that the slowest reader couldn't read yet. Wonderful, kind, amazing woman.) He LOVED his friends. But, he left preschool with a 2nd/3rd grade education... and he was bored and sad.
We let him finish out the year, for the very reason that you state. He had started it, had worked hard (not academically, but in my opinion it's a heck of a lot harder to learn and conform to social rules then it is to learn the academics), had developed relationships that were important to him, and he would have missed out on the celebration & ceremony that his beloved teacher and friends and HE were planning and working towards.
Out of EVERYONE my personal belief is that the goals of children are the most important... because they're Just Learning to set those goals and take the steps necessary to attain them. Yes, there are a hundred ways to work around having to swoop in keep them from finishing them (because, as parents sometimes we have to), but when there is an opportunity for my son to see a goal he's worked for be achieved... I bend over backwards to facilitate that.
After all, we CAN'T be anything that we want to be. We CAN, if we have luck & help, be anything that we work for. I like getting that lesson in young, and building faith before I have to work on building flexibility and an understanding that life happens.
So, obviously, I think you're right on.