Firstly no such thing as a micro pig.
I would agree that there are many pigs, sold as "micro pigs" that actually grow to be quite "macro".
But there are also many, selected for their small size through numerous generations which actually do not grow any bigger than a fat labrador. I have 7. I was given them as "micro pigs", I shall dispose of their offspring as "micro pigs". Surely if I, George and Pepper, and any one else with diminutive sized porcines wish to refer to them as "micro pigs", then why should anyone else wish to question it?