Most households probably aren't watching more than a couple of OTA-sourced programs at once. Surely there are large families that depend largely on OTA that this product wouldn't be a good fit for but for many households, two streams is probably good enough.
To the point I think you were trying to make, it is perhaps misleading that the device has four tuners but can only stream two but it is no less misleading that something like the HR54 (that can't display a UHD stream on its own) can only stream one UHD program at a time yet AT&T will offer you multiple UHD clients.
The TiVo Bolt+ offers six tuners but it will only stream two sessions. The other streaming TiVos can only stream two cable programs.
Bad design shouldn't be transcoding to watch locally. Hdhomerun can record or stream on all tuners and playback on Fire devices. Makes no sense to record Mpeg 2 locally than force transcoding.