I have a Belgian cross too! My guy has licked me a few times before but there is usually an ulterior motive xD Sometimes I am salty, or he drooled on me or I am cooler than him. Like yesterday he was licking my hands because I was holding a cold drink and they were cool and wet. Then he found the drink and started licking the cup instead.
I'm going to have to see some solid proof of this before I buy it. As it's been pointed out, the current record tallest horse is 20. And if you google pictures of him he is an absolute MONSTER. If he is indeed 21 you'd better be calling Guinness. And post pictures for those of us who are skeptical.
In my experience, liking often leads to nipping and biting. So, I'd either discourage it or keep an eye on it so it doesn't escalate.
My gelding is a big hand licker, but he doesn't much care for anything in his face. My foal on the other hand, I trained to give kisses if asked. Keeps his teeth closed and everything, but he likes to kiss on the lips, so there's a good chance he'll slobber both your lips and part of a cheek. Lol
On my first lesson with Oliver I thought he was trying to bite me when he swung his head back while I was trying to brush him, but once I didnt step away and he gave me a wet sloppy kiss! I don't step away anymore, knowing all he want to do is lick me, hahah. :)