Rim weighted whorls do have their uses. This compact spindle was make for producing 6,000 ypp singles while out and about.
In contrast, here is my current production spindle for 9,000 ypp singles:
These spindles do not push the limits. They could be used upside down as bottom whorl spindles. 9,000 ypp singles are plenty strong enough to withstand a half-hitch. Problems with the strength of half-hitches do not show up until higher grists.
Where were such tools when I was learning to spin? Nobody was talking about them and nobody was selling them.