Slitherine

My friend and I are new to Panzer Corps 2 are playing our second PBEM game. Last turn the Russians had a 4 strength point tank. It is was split and became two 4 strength point tanks. I was expecting two 2 strength point tanks. The manual says "split in to two equally sized smaller units". To me the wording is a contradiction. Is this a bug?
In addition if you get two units with the same strength points why not split all your units and double your force? What am I missing?

Sorry, my mistake. My friend just told me that it was an 8 strength point tank that split in to two 4 strength point tanks.