The key word in the report .. after 4 years of painfull investigations .. is "probable"
That's the conspiricy theorist's answer to scientific professionalism.
When all you have are a few smoking (or in this case salt-water corroded) bits of wreckage there is no way you can be 100% definite about any conclusion - even the 737's rudder hard-overs can only "probably" be all associated with a malfunctioning PCU.
Unfortunately, those with axes to grind - or lawyers - interpret this as a license to let their imaginations run riot.