Kingcoon, congratulations on getting your PPR.
Such document requests are routine, not unusual at all. SUV applicants are often asked by IRCC about things like the proof of IP ownership, proof of share ownership among multiple applicants, work experience and study certificates, proof of payments from existing clients, tax returns from your home country and many more as the officer sees fit.
Just having a letter of support/Commitment certificate doesn't mean a home run - it just makes a person or team eligible to apply for SUV. A due diligence process by IRCC will follow. IRCC intends to outsource parts (peer review, entity designation/review) of the SUV screening process soon to private contractors due to the complex nature of the program.