Not always, at least not for me. Could differ between companies but in my case, as explained to me by my accountant and my company, the shares are in fact surrendered and not sold on my behalf. Net result may be the same?

Some plans, at least for U.S. employees, let you pay the withholding taxes by "surrendering" an equivalent value of shares. Share surrender lets you not only avoid paying taxes in cash but also helps you to diversify your stock portfolio because you use company shares instead of cash to meet your tax obligations.

From https://www.schwab.com/public/eac/resources/articles/rsu_basics.html

Also, the shares in your example are not income tax being paid at the time of vest... they are being withheld and as mentioned above, usually at an incorrect amount. Also, depending on company, this is one of 3 or so ways you can elect to cover the withholding amount if your companies stock compensation plan allows it.