Lets not be overly dramatic. You must have a different set of offer terms available to you than what we are privy to but based on whats available to ME and linked to below, there is no problems with what the OP did.
First: https://fi.google.com/about/phones/#phone-prices In big green bold letters at the top "Get the Nexus 5X for $199 when you buy and activate with Project Fi"
From that page, clicking on the text "See Offer Terms" https://fi.google.com/about/faq/#supported-devices-3
"Project Fi is offering a discount of $150 off our normal price for the Nexus 5X, with activation required." (bolding mine)
"You must then activate Fi service on the same account within 30 days of device shipment, or an additional $150 will be charged to your Google Payments account to match the full price of the device." (bolding mine)
And the real kicker (bolding mine again) "There is no minimum activation time needed to be eligible for the discount."
Google spelled out the offer quite well it seems.
The OP did the three things required for the offer...didnt he? If you dont believe he did by all means correct me but he bought the device, he activated the device and then he allowed the device to stay active for X minutes. Was there a step he missed according to the linked offer page?
The reason i dont think they really care is the fact they wanted to move units and clear stock and i dont believe they really lost any money on this promo either. They win either way.