bullshit. You can drop 10lbs, weigh 24hours prior and be back up to your normal before meet starts.
There's 2 trains of thought here. Do it gradually, over 4 to 6 weeks. You will feel better during the meantime and you will probably keep your strength, but you will be hard pressed to make many gains. Cutting weight and getting stronger are hard to do at the same time
Or you can do it drastically. It's tough, but seems to work better on meet day when you have it figured out. For a saturday meet -- start on Sunday and drink water all day adn put salt on everything. You should be drinking maybe 2 gallons or more per day. Do this thru tuesday. On wednseday, just drink water when you are thirsty and cut the salt. Thurs, just enough to choke your food down and none on friday till you weigh in. I also use mild diuretics -- usaully prescription type such as aldactone. I do not like lasix as it's very harsh on your body but aldactone is very mild. Right after you weigh in mix a giant gatorade and pedialyte. Get the unflavored pedialyte because the other stuff tastes like shit. I usally hit the diuretics wed evening thru friday early am. And eat your ass off all day friday. Make sure it is garbage food too -- mroe calories and salt.
The way teh mann says is safer and more sane but you will have more strength on meet day theother way.