I completely agree. But, with baseball's schedule, playing 162 games a year, with all of the travel, ST, etc.. It is ALMOST impossible.
Don't expect a ball player who is only "lifting" 3-4 months a year to get McGwire huge. If you know anything about lifting or body building; an incredibly strict diet, enormous amounts of rest (like 10-12 hrs per day of sleep) and the proper weightlifting can get you pretty huge.
Can someone like McGwire or Sosa do that in 3-4 months and maintain it over 7-8 month baseball season? Highly doubtful. Unless they are maintaining the above training regiment year round (including during the season), any progress that one would make during the 3-4 months of heavy training would surely be depleted by season's end. This is not the NFL with 1 game per week for 16 weeks. This is playing games daily. Incredibly suspect IMO.