Ex addict here. There absolutely is a taste and a smell.
Not many people get to be such high functioning coke users that they take it daily without any hint of a party happening. It’s a party and performance drug. People take it to party longer and harder. Not so they can really concentrate on Killing Eve.
While it's true most people use it in the way you've described, there are high functioning users who take it all day every day. I was one. I am ashamed, I was unwell and I have so many regrets. For me it was a mixture of an abusive childhood, success in business which came with sudden access to my own funds with the addition of bipolar.
People who didn't know about drugs thought I was hyper / manic (because I was) but as I was such a user I wasn't as hyper / manic as one would expect by the point i was using every day.
But to people who have spent time around drugs it was embarrassingly obvious. Always "needing" to nip to the loo, colds / hayfever constantly, urgent calls that required me running outside for five minutes etc.
From what you've said OP it sounds glaringly obvious he's doing coke to me, but I'm conscious I'm ever so aware of it due to my shame about my past and so tend to err on the side of someone doing it rather than giving them the benefit of the doubt.
Just wanted to give my perspective.
Addiction is selfish and you cannot be in a healthy relationship with an addict. I say that from the "other" side of it.
Now I'm happy and stable and can love and be loved. I couldn't have got better while I was with someone, even an angel, you need to have no safe place to land in order to really get well.