My assumption and this article is badly worded. The wording suggests the second group are not treatment-resistant, and considering the loading and expected time

My assumption and this article is badly worded. The wording suggests the second group are not treatment-resistant, and considering the loading and expected timeline of any kind of effect of Escitalopram it may well have been their current medication. Especially as from my experience loading an SSRI has a very unmistakable physical unpleasantness which would be a give-away. There's also the ethical limitations of taking someone off a medication they need for their wellbeing to try something else, which is largely not allowed which makes trialing certain alternatives difficult and complex.