Yes they do start to calm a bit as they get over 6 months and settle!
Just be aware they then go into adolescence soon, and can get very distracted especially with training work already done...
It is such a great feeling when you see training and work paying off though isn't it!
However just to be clear on language -- puppies and even adults aren't actually being 'defiant'
-- especially at a young age, they just don't fully understand the command or understand there is any need to respond. Especially if you repeat it, and change the tone of voice :lol: -- trainers note that a command should only be given once. If you give it several times, the dog learns the command is NEVER 'sit' but 'sit. Puppy, sit. SIT. Come here and SIT. Sit. SIT!' Rememeber all they hear is a set of sounds.
A puppy also will go thru many phases during the first year of being easy to train and quick to respond, and then seeming to ignore people and become indifferent. That's because, like kids, they are young and growing. No one expects children to always do what is wanted on a single word! For dogs even slight variations in tone, wording, or different people giving a command can make them not even understand that a command has been given.
In general puppy training under 6 months is NOT to give a reliable response as it is an unfair expectation -- it is done to set a base on which to build, and because it is fun an useful for owner and puppy.
It will take many many more months and a lifetime of regular -- daily or weekly -- structured practice to get reliable responses and maintain a good level of training in any dog. (same as people with, say, maths. We forget a LOT once weleave school and no longer need to use quadratic equations!).
Ian Dunbar is really good on all these points.
I do think language and terms we use are important as they set up expectations and assumptions that can actually be damaging to training and the relationship between dog and owner. I don't like words like 'defiant' as a puppy is hardly being that, nor are adult dogs -- the issue is almost always one of the dog not actually being fully trained and owners expecting more than the dog can deliver -- which can set up a disappointing relationship on both sides as the dog is labelled a 'problem' or 'stupid'! My trainer friends all say they see this all the time in their classes when actually the people have a wonderful, smart responsive dog/pup that simply gets conflicting messages or isn't actually trained fully.