I wouldn't be surprised if it were true. He was a huge dude!
From Wikipedia :
” Born on August 3, 1934, William Dee Calhoun grew up on a farm in McKinney, Texas; a rural suburb located in Collin County, about 30 miles north of Dallas. William was an unusually large child with an extraordinary appetite (it was said that he regularly ate a dozen eggs for breakfast); and by age 14, he already weighed 300 pounds. “
Maybe it WASn’t a myth after all !