Might be. It's hard to know and be 100% sure about an identity. If you run into an unidentified clem you want to buy in the future you can ask the manager of the plant department for the names of the clematises they bought. That could help with identification.
Yes it seems like it blooms earlier than some of my others. I'm pretty sure it must be that, don't know if it survived the move to my mom's place though or not. But with a name I can at least replace it, that is, it will look like it even if by chance it isn't just exactly that one.