People like being told they are right, and when a response contains that formulation, on average, given the choice, people will pick it more often than a response that doesn't, and the LLM will adapt.
Also, you just when you say the word "genuine" was in there `43` times. In actuality, I counted only 46 instances, far lower than the number you gave.
I, too, notice a lot of differences in style between these two applications, so it may very well be due to the system prompt.
But it's a game of whackamole really, and already I'm sure I'm reading and engaging with some double-digit percentage of entirely AI-written text without realising it.
Four "but also"s, one "not only", two "not just"s, but never in conjunction, which would be a really easy telltale.
Zero "and also"s, which is what I frequently write, as a human, non english-native speaker.
Verdict: likely AI slop?