That is not true...my son's worked on lobster boats and sometimes we got some big ones...and when they scuba dived, i have pictures of BIG lobsters they caught...we ate them the day caught and it was sweet and tender...we expected leather...but we all had a meal and my husband and i continued to eat left over the next day...it was good.
When lobster sits in tanks they dont get fed their body shrinks and they lose the sweetness and became tough.