Oh yes everytime. When you know what you "have" to say, the pressure is higher. Like when you read. Or have the right answer to a question in class. You can't always use synonyms that feel easier to speak. With free speech or something you don't have to think too much beforehand, you can always change the word, restart the whole sentence with a different beginning. Doing fake pauses. Having all these opportunities reduce the stresslevel, which has an positive impact on your stutter.