The widespread Theta II engine problem is rod bearing failure.
The OP has failure due to sludge.
These are two different problems.
I’ve seen many complaints online about the Theta II, and no others have mentioned sludge.
If the inside surfaces of the OP’s engine are coated with sludge, it’s due to one or more of these reasons:
Oil change interval (time or mileage) too long for the operating conditions.
Chronically low oil level. Remaining oil “overworked”.
Low quality oil didn’t meet required spec.
PCV system failure caused excessive oil contamination.