I have seen American, British and Japanese fuel lines disintegrate under E10 (and in California, the methanol used before it). Until *very* recently, most fuel line was not rated for or particularly tolerant of ethanol.
Also, it’s not just “shitty Chinese engines” as both Bombardier and Mercury Marine have outright said for many of their models that any amount of alcohol can harm them.
Where are they sourcing their polymer parts from?
Chinese stuff is everywhere.
Some of the worst offenders are Weedeater - US engine, carbs from China.