Yes, but assuming your shares continue to appreciate at a faster rate than the interest you can defer any tax payments so far into the future that the amount becomes more and more insignificant due to economic inflation and capital appreciation.

You're right that you still have to pay the tax, but you pay it on far more favourable terms than the average person. Of course the flip side of this is that the price of your shares collapse, but typically these secured loans are a fraction of an individuals net-worth and the risk is very low.

Edit: I should add you can also time when you're taxed. So for example if taxes in the present are high you can wait then realise any profits when they're lower.