Even though you can't lift the 600 lb object it's still in the correct ballpark for illustrative purposes when dealing with orders of magnitude.

In a similar vein a 20 gallon fishtank and a small bathtub are approximately the same despite that I can't actually fit in the 20 gallon fishtank myself.

It's also the difference between 1lb and 6lbs also, so the analogy isn't perfect. The problem is that once you approach the limits of the average human ability, multipliers can transform something possible into something impossible.

I'm pretty sure I could feel one sixth of a mosquito hit me, because I've been pelted by much smaller gnats before!

(It does depend on where, of course.)