EDIT: I also plan to utilize the Roth ladder in early retirement, and understand having a standing traditional IRA balance could mess things up?
No. The
article you reference (which is a very good one) is talking about "backdoor" Roth conversions, not the
"Roth IRA Conversion Ladder" that you'll want to be doing in retirement.
They're really the same thing, with the same tax effects, but the expectations are different, and the expectations are what matters here.
In both cases, you're converting a portion of a Traditional IRA into a Roth IRA, and you're taxed on the amount of Traditional pre-tax money that you're converting.
In the "conversion ladder", you're completely expecting to be taxed on the conversion (though you expect the tax to be at a low rate), so it's no big deal.
But in the "backdoor", you're expecting no tax on the conversion. If you want to do a "backdoor" conversion in the first place, that means you have income that puts you in a fairly high tax-bracket, so it generally doesn't make sense to do a conversion at that time if you're going to be taxed on it. And if you don't have any pre-tax IRA money, you will not be taxed, because the "backdoor" conversion converts
post-tax Traditional IRA money into Roth IRA money. That's the case under which the "backdoor" conversion makes sense. However, if you have a separate pre-tax IRA, then you must pay tax on the "backdoor" conversion even if in your mind the conversion amount came from your post-tax money; in the IRS's mind, it came from the combination of your pre-tax and post-tax money, and is taxed accordingly.
So while a pre-tax Traditional IRA won't mess up the Roth conversion ladder, it
can prevent "backdoor" Roth conversions that you might want to do in the future. I don't really know if that's a strong enough reason to avoid creating a pre-tax IRA pot right now, but I think it probably isn't in most cases.