I've never heard this before. I've always maintained the same watering schedule whether blooming or not. Is this a rumor started by the "water your Phaleanopsis with ice-cubes" people?
I don't think so, unless the roots are in danger of rotting. You want to keep the roots happy. Many orchids die because people overwater them or the medium doesn't provide enough air around the roots/the medium stays too wet. The medium's purpose is to hold humid air around the roots, just like in the tropical places where they grow, not to keep the roots watered, as with my lotus. I hope that helps. Good luck with your orchid!
Romina, There is no need to adjust your watering schedule and you should continue to water when your potting mix becomes somewhat dry. Your roots should be silvery gray not green when you do.
Watering your phal less when in bloom will do just the opposite, you'll find they wilt much sooner nevermind you are depriving your plant of needed moisture to keep the leaves firm and healthy.