That article is from August 22 - I just checked in the MAS and the most recent Airmail update was the 25th and the changes specifically mention a URL security fix, so they may have addressed this already.

I've also used Airmail on and off for years and quite like it, on both Mac and iOS. Mail.app isn't bad, but I've used labels heavily for years, including multiple labels on emails, and Mail doesn't seem to handle that scenario very well.