Is following true or false?

This answer is incorrect. The time required to reach sterilization using a high-level disinfectant is absolutely longer than the time required to reach disinfection.

Direct from IAHCSMM's Central Service Technical Manual:
"Glutaraldehyde is a high-level disinfectant used for semi-critical devices such as endoscopes and ultrasonic probes used in radiology. Conditions including times and temperatures for its use as a high-level disinfectant vary by manufacturer, and it is always best to consult the product's manufacturer for this information. The time for sterilization is extended to 10 hours or more depending upon the concentration and the manufacturer's recommendations."

OPA is not classified as a sterilant, and I do not believe Formaldehyde is either.

Glutaraldehyde's time to achieve high-level disinfection (as per a few manufacturers I've consulted): ~25 minutes
Glutaraldehyde's time to achieve sterilization (as per a few manufacturers I've consulted): ~10 hours

Seems like a pretty substantial time difference to me.