Don't know which products actually implement them, but a bunch of antenna designers offer spec designs with their logo for free, and can do custom ones upon request. The problem is that you necessarily sacrifice performance for vanity; these designs generally create undesirable radiation patterns.
I actually wanted to broaden the bandwidth of the planar inverted F antenna patch bit; it was too peaky and narrow. I experimented with about four or five variants of the logo until I found one that had the desired effect. So it is true, the peak gain is reduced by this, but the gain in bandwidth meant I had better average gain over the entire 2.4G band.
Unfortunately, I can't definitively explain why it was better beyond some theoretical platitudes -- in the end, it was literally a process of just making educated guesses and measuring stuff until I found something that worked.
I've tried modelling software in the past, but the results don't match well with measurement, and the paid licenses for modelling software are by far more expensive than the cost of copper tape and a good knife, and then running a few prototypes (and the free stuff I could find wasn't even close to meeting the task). Not to mention the time -- the sims take a long time to run, and building accurate models is also quite time consuming.
Sort of a dissatisfying reality, but that's how the sausage got made.
The conventional wisdom in ham circles is that thicker elements result in broader bandwidth. That goes along nicely with structural stiffness, and thus most VHF Yagi-Uda antennae are made with their elements cut from tube instead of rod, for example.
I'm not sure which changes you made exactly, but I wouldn't be surprised if the end effect was thickening the relevant portions.
