In the case of any mix by Steven Wilson, the Atmos mix is derived from the 5.1 and not vice-versa. For his first attempt in The Future Bites, he brought the 5.1 mix to Dolby engineer Jake Fields who assisted him in mixing up to Atmos. In the case of the Tipping Point it appears he has done it on his own (he's done a few more Atmos mixes since last year) but the Atmos is again derived from the 5.1.There are so few Atmos releases with a dedicated 5.1 mix that it doesn't matter much at this point.
I would be surprised if much effort went into these. There is an option in the Atmos mixing software to output a 5.1 mix. My guess it that is what is used most of the time. The Tipping Point may be different, and more effort was used for the 5.1 mix.
I agree though that in the case of all the direct to streaming mixes, it's really just Atmos. In these cases the real issue is whether the engineer knows how to mix into surround at all.