These exceptions were intended to be exceptions, not the rule. Obviously United is "cracking down" not because they despise GS members, but because the informal blogosphere publication of "rules" surrounding these exceptions (such J>2) is creating expectations, and ultimately displacing revenue. Before the new restrictions kicked in, some savvy GS members were probably using the "exceptions" more like a "business class companion pass" with "coach fare co-pay". Most probably weren't. Most GS members fly a lot alone on expensive fares and occasionally want to take a family member along for the ride.
But seriously, if a flight on a route is routinely showing J4 C0-- or even J6 C0-- and the same GS member routinely snags forced seats on that flight/route for a companion (which is a realistic hypothetical), that one GS member could end up displacing significant revenue, flight after flight. The "half-roundtrip" rule at least puts some skin back in the game-- in other words, no more roundtrip "business class companion pass" with "coach fare co-pay".
It is a shame that a few savvy GS members likely decided to game the system over and over again and abuse what were truly intended to be exceptions in a way that obviously ended up being sufficiently damaging to United's bottom line that they had to start saying "no" to all GS members. Don't think for a moment that United likes saying "no" to any GS member request.