Ok........slow down a second hun.
Everyone think about this a second.
Does anyone EVER connect with ANYONE else in the same way with the same intensity ? You with me here ?
All 3 of you need to talk about this - and bunches of other general human traits - so you don't start micro-analyzing everything.
If they-as a couple-have some pie in the sky goal of having some relationship where everyone is EQUALLY bonkers over each other, and compatible in all the zillions of other little life preferences, I suggest they invest in a rocket and find another planet and species
It ain't happening !
Add to that, things evolve. As RP and others have said maybe in a somewhat different way, there's NRE involved here which will have to pass before you can see the true colors of anything. You may walk in tomorrow and the situation will change the chemistry between all of you. Then it will happen again some time in the future. Always in flux.
I say - drop the expectations and just live it - in the moment. Celebrate the differences in the way you connect to each - and how they connect to each other. If you can do that in a loving manner it will all fall into place.