What would be the logical reason for not soldering it? Use and high heat gun and solder it quick. Just stick the wire through the loop and don't wrap it so it can be removed easily. It is not always heat that does damage, it is the amount of time that heat is applied and I think that is Briggs thinking on that subject. If it is not soldered it is a loose connection, and loose connections build resistance. Resistance causes failure.
I think B&S is concerned about either too much solder wicking into the plug wire making it brittle and prone to breakage caused by vibration, or over-heating the coil during soldering.
Soldering also means de-soldering when the wire needs replacement.
However, B&S recommends tinning the wire before crimping it on to the terminal.
I have seen many engines where the connection was soldered without any problems, and I believe many came from the factory soldered..