I don't believe there is any significance to the 10 round limit in the past. I believe it is simply (as others say) a stepping stone to NONE. "No guns" was too big a bite for liberals to swallow before, and becoming more palatable to them now.
It was acceptable to the Government as a "first step" to the real interest to reduce it to zero incrementally. These baby steps have become Governments defined "common sense", as a means of circumventing the Constitution, and many have bought into it.
Soon the mag limit will be zero, if we let it.
"Peace is that brief, glorious moment in history when everybody stands around reloading". Anonymous
Earp: Not everyone who knows you hates you.
DOC: I know it ain't always easy bein' my friend....but I'll BE THERE when you need me.