Reasoning behind it - galvanic corrosion when two types of metals are in contact with each other (as we all know), and an electrolyte (humidity / rainwater/ sea or salt water etc). Alloy calipers are made from an aluminim alloy I understand, and this corrosion requires an anode and cathode to start the process, if the two metals are similar this process is reduced.
Unfortunately stainless steel and aluminium alloy are more prone to electron transfer, and titanium even more so; mild steel or zinc plated steel less so. In other words the more similar the metal are between anode and cathode, the less galvanic corrosion occurs.
You would have thought the engineers at Brembo would fit the most appropriate bleed nipples for the metal in their calipers, so with that in mind, I am going to stick with their standard bleed nipples. I'm not saying galvanic corrosion won't occur again, but with a barrier on the threads such as ceramic grease or red rubber grease (being unaffected by brake fluid) should help to reduce the effect.
Took some research but stainless in alloy, and titanium in alloy are not recommended at all unless sleeved with a more compatible metal.
Now have to get the snapped and seized bleed nipples out......
