The underlying points are correct: stocks lose less of their value to taxes each year, but since stocks are expected to grow faster than bonds, they will eventually lose more of their total value. If your time horizon is long enough, then it is better to tax-defer stocks. However, with most assumptions, "long enough" is more than your lifetime.
The article made two unreasonable assumptions which favor stocks in tax-deferred. It assumed a 15% growth rate for stocks, which is far above the historical rate. And it understated the amount of tax deferral you can get with an index fund: if stocks have a 2% yield, the tax is 0.40% each year (with their assumed 20% combined tax rate), and the capital-gains tax when you sell can be divided by the full number of years you hold the stocks, for an effective rate likely to be about 0.7%.
It also made two assumptions which favor bonds in tax-deferred. Bonds are assumed to have 5% yield, which is historically reasonable but far above current rates. And if you hold bonds in a taxable account in a 40% combined tax bracket, you wouldn't hold corporate bonds taxed at 40%, but municipal bonds, probably from your own state. Given current yields, it might actually make sense to put municipal bonds in a taxable account, with the intention of switching (and selling the bonds for a capital loss) when rates rise.
The third point, about losing the tax deferral when you sell bonds, doesn't make sense.
Given that you use your bonds whenever there are stock declines (assumption #1 at the top), as soon as you experience a stock decline, you would withdraw the money, and would not be able to put it back in. This would result in losing the retirement account tax benefit forever, due to a single stock decline.
And you lose the same benefit if your retirement account is all stocks and you sell stocks from that account during a rising market.
There is a sophistication that can help you get around this limitation, but is not very practical due to its complexity and excessive trading:
Say you need $10k from bonds during a stock decline. You can do the following:
Taxable account: sell $10k stocks
Retirement account: sell $10k bonds, buy $10k stocks
Once your stock portfolio recovers, you can move the stocks in the retirement account back to bonds (sell $10k stocks, buy $10k bonds)
This is only "excessive trading" if you have a lot of different individual bonds and stocks. If you have a bond fund, or a bond portfolio of Treasuries, you can sell bonds and buy a stock index fund or ETF in your IRA with a few mouse clicks.