This has always been the case.
Don't use security-threatening words lightly, in security-sensitive situations.
Besides, just using the word would only trigger the Air Marshal to tell you to calm down and clarify what you meant.
To get the full Air Marshal Treatment, you'd need to repeat the word bomb multiple times, move around when ordered to be still, attempt to avoid the Air Marshals who are trying to remain in contact with you, and making threatening gestures that imply your willingness and ability to kill large numbers of people.
I mean, you have to work pretty hard to get an Air Marshal to actually kill you.
Mostly, they'll just take you aside and make your life miserable for a few hours--probably causing you to miss your flight--as punishment for being an asshat.