I am aware of at least one company which does this from my consulting days, and would caution you that what you get in perceived security benefits from making sure that tenants can't interact with each others' data you'll give back many times over with engineering complexity, operational issues, and substantial pain to resolve ~trivial questions.

I also tend to think that the security benefit is more theatre than reality. If an adversary compromises an employee laptop or gets RCE on the web tier (etc, etc), they'll get all the databases regardless of whose account (if any) they started with.

(The way I generally deal with this in a cross-tenant application is to ban, in Rails parlance, Model.find(...) unless the model is whitelisted (non-customer-specific). All access to customer-specific data is through @current_account.models.find(...) or Model.dangerously_find_across_accounts(...) for e.g. internal admin dashboards. One can audit new uses of dangerously_ methods, restrict them to particular parts of the codebase via testing or metaprogramming magic, etc.