Of course, it may be that it all came down to support contracts internally between Google and the Nexus device suppliers (the Nexus 7 blobs come via Asus, the Nexus 4 was an LG device that used the same Qualcomm chipset IIRC.) but that’s the kind of detail that end users really don’t care about: both were Google devices that Google sold & from the point of view of the end user Google dropped support for one device for no obvious reason as far as the end user can see.
