“His first tip about smashing the burger is insane. You’ll squeeze all the juice out of it and it will be dry as hell.”
Indeed. Every restaurant and cooking show explains why mashing the burger on the flat top will cause exactly what you describe. The other big no-no is to cover burger on the flat top as that will cause if to steam instead of grill.
BTW, the REAL number one tip is to use freshly ground hamburger made from fresh, high-quality cuts of beef you select yourself and have custom ground on the spot (or even grind it yourself), and then cook the fresh hamburger within a few hours of its being ground.
Personally, I prefer 100% ground chuck hamburger.
If you do the smash right as you put the meat on a hot griddle the fat hasn’t had time to melt yet to leak out. What you are getting is the outside char. If you smash a partially cooked burger, than yes you are losing juice.
Ground chuck burgers are delicious. I ask the butcher for the trimmed fat cap from Prime Rib. Grind that to a ratio of 70/30. Heaven on a bun!