True

> It doesn't matter if they use dollars, bitcoins, or bushels of corn.

Or, say, personal information that can be used in targeting advertising.

> Nearly all users of Google are NOT customers

I'd describe them a suppliers, but unless you've suddenly decided that, contrary your early statement, it does matter what they provide in exchange for the services they receive, they can also, by your logic, be described accurately as "customers".

> and indeed do form part of the product offering, as the OP stated

No, the users do not form part of the product offering; the slave trade is not part of Google's business models.

They are suppliers of inputs (both information used in targeting advertising, and the advertising opportunities through which the actual advertising is delivered being the key pair of inputs) that are used in Google's product offerings; insofar as these inputs are exchanged for services Google provides rather than for cash payment, they are also customers purchasing those services in a non-cash exchange.