Actually, dynamic and static are opposites. Static is a synonym for "fixed". Technically, in your examples, all of the situations you describe are with a dynamic IP. Even if the IP address changes every few months, it's still considered a dynamic IP. It sounds strange, I know.because DSL gives you Dynamic / Static or whatever its called IP.
How your ISP does things seems very convenient - I wish I could do that! But, it isn't really related to the technology - it's more based on the features that your particular ISP decided to provide, or the manor in which they run their DHCP server. (My DSL ISP doesn't do that for example.)
Edit: Which ISP is this? That information might be useful to have
PS - Coke vs. Pepsi, absolutely!