I don't think PS really used it for base PS4, but at that time PS themselves weren't really pushing the power narrative. Yet PS used it for Pro, after XB already started using it for Project Scorpio and will use it again if Anaconda has weaker performance on paper. After the marketing push MS had behind XB1X using this slogan, PS will surely want to throw it in the face of MS since that's one of the things their customers have been using to justify remaining on the XB platform.
It's hard to believe MS will go above $499, but if the two SKU approach is true, they could very well get away with it, especially if PS5 is in fact $499 at launch. If you have a $499 PS5, then MS can launch Lockhart anywhere from $299-$399, and they can launch Anaconda at $599. If Lockhart were 6TF give or take, at $399, it would fall right into place where XB1X would have dropped to next, which is the "sweet spot". That should lead to much better sales for Lockhart in comparison to XB1, which means it doesn't really matter who buys Anaconda, just as long as enough are sold to make the upper tier worth it going forward. Even if Anaconda didn't sell much, it would still allow MS the bragging rights and marketing to be able to say we have the strongest hardware on the market, even if it's only say 10% of total next gen sales.
If this is the case, it will be interesting to see what PS does, and whether or not they drop $50 or so to try and better compete in terms of price with Lockhart, because there won't be anything they can do to compete with a $599 Anaconda aside from large multi game bundles.
On the other hand, if Lockhart was $299-$349, and Anaconda is $500-$600, then it very well may be in the best interest of PS to keep the price of PS5 higher at $499 if possible. This would be done to make customers question Lockhart. If you're buying a next gen console, and one is $299, and the other two are $499 or higher, your going to ask yourself which one is out of place and does it belong? If PS only has one console at $499, and MS also has one around that price, but they also have a $299 SKU, is it really going to cut it? Is it going to lead to buying $100 or more in accessories down the line to make up for the initial low price? If PS5 is expensive enough to manufacture that they can't bring the single SKU price down to compete with Lockhart, then keeping the price up around Anaconda will give them the best chance of consumers passing up on Lockhart for the next step up in price, which would be PS5.
If they aim to copy the features that Sony announced, such as load times being near nonexistent and ray tracing HW, in both SKUs, my guess is the Lockhart is going to be $399. This means that the PS5 is going to be just $100 more for a system that is 3x the power, if leaks are accurate. And with PS5 being B/C with the PS4, I see most people who gamed on the PS4, sticking with the PS5, since they can sell their PS4s and get a system that plays both last gen and next gen games. In this case, I really don't see the Lockhart selling any better than the XBO. There were times when the XBO was on sale for $50+ less than the PS4, yet that still didn't change its fortunes, or even cause it to outsell the PS4 in the XBO's strongest market, the US. And that was against a system that was ~40% more powerful. This would be one that is 200% more powerful if the 4Tflops leak is accurate. God help them if Sony takes a bigger hit and sell for $449. Or if by some magic they still hit that $399 price.
The only way I think MS can sell the Lockhart at $299 is if they either take a huge loss, which MS has shown this gen they really don't have much interest in, or it lacks quite a few features that Sony is making standard next gen for consoles, i.e. ray tracing HW and a SSD to practically eliminate load times, as well as 4K (at least 4K CB for the more graphic intensive games.) At that point, you are correct, and people are going to start wondering what's lacking in the Lockhart to make it that low. Of course, that will be the general consumer audience. The core gamers that make up the majority of early adopters will already know the deal with the Lockhart and will avoid it like the plague. They will want a real jump over this gen, not a half-step that seems almost pointless.