Most people, however monodextrous (is that a word?!) they are, find that the rudimentary thumb/finger action needed to scroll on a phone is no easier on their dominant hand than their recessive one.
Do you only ever touch your face or head with your dominant hand? I don't mean something that requires motor skills, like brushing your teeth or hair (with a brush), but if you were scratching an itch, shielding your eyes to see ahead in bright sunlight, removing a stray hair or moving your hair out of your eyes, adjusting your glasses or, erm, 'manually decongesting' your nostrils(!) etc. I can only speak statistically-insignificantly for myself, however I'm strictly right-handed where strength and motor-skills are required, but I've noticed that I definitely tend to (unconsciously) favour my left hand/arm when I need to touch my face.
Same as when typing: whereas you likely find handwriting comfortably/neatly with a pen far easier with your dominant hand, do you use a keyboard (physical or on-screen) based on which hand is dominant or simply based on which hand is nearer to the key/button you need to press?
Also, if you were finger-tip-writing in snow or misted-up glass (or similar), you would likely find you could do it a bit faster with your dominant hand, but that you would find it no less comfortable and produce writing that was no less legible if you used your (slightly slower) less-dominant hand.