I'm not sure the basis for many things stated in the Paterek manual. I started reading it once, and when I reached about 4 things I considered to be myths, I closed the book and gave it back to the guy I borrowed it from.
In the case of the 1.0 walled head tube, these are my observations and experience. First, you don't have a lot of choice in tubes for a 1" steerer, but thicker ones are available.
So... I have FBed tubes to the thinner head tube stock. The tubes you are joining to the head tube are thinner, so strength of the tube is not really the issue. I've never seen one tear from the head tube. But, due to the higher heat required, distortion is much greater. Reinforcement rings will help (not with distortion) but give you extra material for reaming. It's surprising how much distortion there really is in the HAZ. If your fillet isn't humongous it won't spread too far.
One thing I do is leave enough material above and below where the tubes join so no material is removed from the weld areas resulting in a thinner tube at that spot. And... I think reinforcement rings are necessary, especially in the 1.0 walled tubes.
JMO- someone may come along and say I'm all wet, but that's OK. It's just what I see. Not comfortable? Get a thicker tube.