That was my second guess...
I'll admit I'm having trouble figuring out why you'd need stiffer swaybar bushings or endlinks.
The swaybar is a spring (a torsion bar, actually,) between the two sides of the suspension. Movement in both sides is not resisted. Movement in only one side causes the bar to resist that movement, since it's trying to compress the other side's suspension.
So since the bar is essentially a spring, any compliance in the endlinks or the bushings will be seen as a lower spring rate, initially. Once the endlinks and/or bushings have fully compressed, the bar starts twisting and the effective spring rate goes up -- you have, in effect, a progressive-rate spring.
The upshot of that would be, in my eyes, a bit more body roll, and a bit longer time required for the chassis to take a set on the corners -- but only a bit.
And seeing how some body roll is good, 'cause us humans seem to like it (driving a car with no body roll tends to be some=what more difficult -- our brains seem to want at least a little roll, apparently,) having a little compliance in the end links and bushings probably isn't all that bad.
My AI car runs factory bushings and Energy Suspension end links, only because the ES links are somewhat adjustable (cut the tube,) and the factory links aren't.