Actually, there is a crystal clear difference between chamberblocking intentionally and getting lucky chambers. The difference is that the latter results from spamming attacks haphazardly hoping to either double hit or chamberblock while the former happens as a deliberate and timed use of the attack animation instead of blocking, in a controlled environment. Some situations make it barely possible to chamberblock something deliberately, such as your enemy feinting or holding. That said, lucky chambers are very rare. It takes a lack of skill and a large amount of potato-based alcohol and vowels in your native language to intentionally run around liberally swinging bardiches in a full suit of heavy armor, hoping to get lucky chambers. The heavy armor, high damage weapon and lack of skill are required in order to make the risk/reward trade-off of hoping for lucky chambers while spamming actually worthwhile.