You're making lots of assumptions and leaps about Google. Like anyone else all they can do is map SSID to a general locality. They still dont know who you are based on that single piece of information.
The question is - is an SSID personal data.
No. It isnt.
Is a MAC? Potentially but only to a very specific and small number of entities. And then as I said for it to be personal data the link between that device and you has to be realistically and reasonably likely to occur.
Like I said, you've already decided you're correct and this is a breach. I look forward to reading the result of your court case against Karcher in 3 years time, so don't forget to come back and let us know how you get on