I would expect that every keyboard of that size has a function layer since there's a perfect spot for the FN key in the lower right. What would expect to be in that place instead?
Do you have a specific issue with an FN key, or are you looking for minimal for the sake of minimal?
The "extended lifetime warranty" likely only covers factory defects, not normal wear and tear. If you use it for 5 years and it dies, the company will probably just claim it is normal wear and not cover anything. The word "lifetime" is also subjective.