That's false. You can figure out out directly.
Paying your own social security tax: +7.5% (say $7500 out of $100k salary) Health Insurance: $700-$1000 per month (say $12k annually) 2 weeks paid vacation + paid holidays: +7% (another $7000 out of $100k salary)
So, $100k contractor is equivalent to ~$80k as a full-time employee with benefits.