This is only true if you "sell" 40 shares immediately at the time of vesting to pay the tax bill. Because you lose the 40 shares, you don't have as much shares to appreciate in the subsequent upswing. However if you prefer to settle your tax obligations in cash instead, you don't have this issue and you'd actually pay less taxes (assuming the upswing does materialize). It's risky though, because you're basically taking a long position on the stock, and if it falls even more, you'd lose even more money.

You could also see that it's odd in that most companies from 100 years ago simply don't exist. The perfectly flat trajectory bordering on fade-out is uncommon. The median 100-year-old tech company is Sperry, not IBM.