Yup, I've seen that too. I even tried to follow the code that sets that splitter once, and it was called like 5 times on start. IIRC, only the first 2 times was called with the right size, but the next calls used a different one... which finally became the size you see in "After".
I'm not completely sure, but I think it worked correctly some time ago. I even recall seeing something in the commit logs. I remember trying that version, and it didn't solve the problem. Chances are it was something else and I
misinterpreted (Firefox's spell checker says it's correctly written, so it must mean something
it.