Many old wive's tales contain some elements of truth. These contain very few. The meat version is especially widespread and pernicious.
There's some controversy about when to add salt regarding long dry "marinades," as, for instance, in using rubs for competition barbecue. However, salting your meat a few minutes before hitting the pan with it will not cause it to bleed out faster than it would ordinarily -- at least not fast enough to notice. It will make a sight improvement in developing fond, and a rather larger improvement in developing "crust," i.e., the meat's surface texture resulting from searing. Nearly all professional chefs salt meat before browning or searing and steaks before cooking.
The best way to tell is to cut a steak in half, season one before and after (if necessary) cooking and the other after only.
When cooking steak, I intentionally draw a little moisture from the meat by using a brief marinade (20 minutes or so) in a tablespoon or two of red wine and worcestershire sauce in order to create a "syrup" of meat juices and marinade to "glue" the rub to the meat. Try 1 tbs of each for two pounds of steak, and you'll end up with less than 2-1/2 tbs of a very thick liquid. Two pounds of steak can afford to lose 1 tsp moisture in exchange for the benefits. Most people lose a lot more by not properly resting the meat anyway.
Worth another experiment?
Vegetables should always be boiled in salted water, because they taste better and there is no known nutritional difference. My pontification aside, simply cook two pots and see which you like better. Huge difference.
Finally -- use kosher salt if possible for salting meat before cooking because it adheres to the meat better and does not dissolve as easily as table salt. Use ordinary table salt for cooking anything in solution. It dissolves more easily and completely, costs less, and taste the same once dissolved. Use whatever you like for "finishing" and at the table. Exotic salts bring slightly different tastes and are fun to play with.
My dos centavos,