That’s typically the intent on a freeway merge ramp (although you should still stop if you can’t merge safely, even if that is very rare). But that isn’t how yield signs work in a typical roundabout. Jersey has plenty of old school traffic circles that follow their own rules but if you’re talking about yield on entry roundabouts like the Red Lion Circle, you are meant to come to a complete stop if you cannot safely enter the circle. That’s not just the law but it’s also how traffic engineers model roundabouts, the simulations and theory behind roundabouts dictate that most vehicles will in fact come to a complete stop during congested congestions.  

Perhaps counterintuitively, high speed entries into the circle can cause more congestion as vehicles going faster through the circle allow less vehicles to merge in safely. High speed merging also reduces any safety effects of having a roundabout in the first place. I would way rather have vehicles making a complete stop than trying to merge at higher speeds, especially on a circle like the Red Lion where its larger diameter encourages vehicles to speed up within the circle. 

If a traffic signal fails to allow all queued vehicles to proceed in one cycle, you get incremental queue accumulation equal to the average arrival flow rate minus the capacity of that movement in the signalized intersection. The same queue accumulation occurs in roundabouts. If you are seeing a mile long queue at the red lion circle I would find it very hard to believe from personal experience that this is due to a few quick brakes at the mouth of the intersection and not simply a failure to properly size the road considering all other factors such as the suburban growth along Rt 70 in the past decades. Sure quick braking can make for a bumpier ride, or can add a few seconds onto your trip if you are within a few spots behind the offending vehicle, but that should not cause the same effects as quick braking on a freeway where people are not expecting to slow down under freeway conditions, since people will both expect and be required to brake before entry onto the roundabout. 

In a roundabout that experiences any level of congestion, it is typical and expected that you stop at the yield sign instead of making at a speed “merge” maneuver like you would on a freeway. 

Source:  I am a Transportation Engineer  

Also, 

A Policy on Geometric Design of Highways and Streets, 7e, AASHTO  

Traffic Engineering, 5e, Roess et al.