Consider it this way: if a non-profit pays a for-profit company for services rendered (pure expense on the balance sheet), are they "passing on" your donation to the for-profit? I would think not. Non-profits need to be able to pay for things. At the most basic office-management level, they would need to rent office space, buy paper and coffee filters, contract a janitorial service, etc.

Would there be a limit? I don't think so. If I was running, say, a non-profit website host, 100% of my raised donations would be going, as expenses, to a for-profit company (some commercial cloud-hosting provider.) That's still an entirely-legitimate model for a non-profit to operate under.