Often people refuse to understand the difference between different types of intellectual property rights. The % change "rule" is about copyright. It has nothing to do with patent rights at all. Its been bandied about in reference to copyright that if you change 10% its not a violation, but that has not been a hard and fast rule in legal practice. I think its a an artifact of people not wanting to take a few extra minutes to understand the truth and their desire to find a short cut or easier answer. There have been lawsuits over just the melody in a song even when the lyrics have been totally different. 10% is not a hard rule, and it doesn't really apply to patents at all.
A patent is a grant of exclusion for an idea about something. You can change 99%, but if it still corporates the patented concept or idea it is still a violation of the patent. It might look 99% the same and not incorporate any of the elements of the patent. Then its not a violation of a patent.
Example: A Larew Salt Craw (tm) doesn't look anything like a Yamamoto Senko (tm) but they both incorporated the idea of "infusing salt into a soft plastic bait."