The heavy weight DOES compress the spine and joints. Arnold used to be almost 6'2" and is struggling with 5'11" today. Big Louie used to be over 6'4" and is between 6'2" and 6'3" today. Geoff Capes (British strongman) used to be 6'6" and today is barely taller than 6'0" MMA fighter. Even Reg Park was once 6'1" and was about 5'9" when he died. The list goes on and on.
people lose height as they age, period. My father and granfather are both around 2-4" shorter than they were in their 20s.
connective tissues wear and compress, fatigue and constant movement erodes bone..... its natural. Youre going to get shorter as you get ilded, I dont know if heavy deads or squats are really going to accelerate it that much.