No, there is no way to change the increment to only 1 when using a remote.

You can achieve increase or decreases by 1 using Sonos Voice Control, by saying “hey Sonos, increase volume by 1” 

Not sure if your problem is only with the volume taking steps of two or that the steps itself are too big. I'm surprised Sony TV's show steps at all. My Samsung TV's only show volume up or down.

Since this seems Sony-related you could also ask Sony.

You can also ask SVC to set “Volume to 12”

I used to have a Sony TV some years ago and added the Sony’s own HT-AS5 home theatre surround system and that too had volume increments of 2 for each button press on the remote and no way to change that - so I’m thinking it’s just the way the Sony TV’s (and some others) may perhaps work.

LG C1 also has increments of 2 when increasing/decreasing volume, evidenced by volume slider in Sonos app.

I think my previous Samsung changed it by 4 (but could be wrong on this)

Changing it to 1 increment would likely lead to complaints that the change is not sufficient enough.

SVC for instance changes it by 8 if you ask for an increase/decrease in volume.

By 8 is way too much, imho :)

If i disconnect the Sonos Arc, the Sony TV does step in increments of 1, it’s only when it’s connected to the Sonos does it step in increments of 2. I thought maybe it was the TV receiving the IR signal and the Sonos receiving the IR signal and both increasing the volume. But I didn’t see a way to test my theory. Does the Sonos Arc even have an IR receiver? Can I turn it off?

Yes, the Sonos app includes specific system settings for the Arc where you can enable/disable its IR.