I see that as well: on the portfolio page of Vanguard Total Stock Market, "Tesla Inc" joins 9 other companies that fit between Yahoo! Inc and Haliburton Co. But peek at the S&P 500 list, and only 2 companies are between them. Up to Standard & Poor's, I suppose.
The Total Stock Market overlaps the S&P 500 about 72%. Their performance tends to be similar in practice. I favor having the small and mid cap stocks as well, not just the S&P 500, but indexing at low cost is more important than that distinction.