On what basis are you making statements like this? Where does it say on any Canadian website that you have had to have worked in the province for 1.5 years before leaving? Please provide proof.
OP your answer is simple: no. The point of PNP programs is to bring economic benefits, people, and skills to the province that nominated you. You must fulfill your obligations to Ontario and genuinely live there while your PR is being processed. After you have PR you can do whatever you want.
For any other special circumstances, such as doing fieldwork/assignments or being re-posted to an Ontario employer's office elsewhere, you are best off asking the OINP and getting the answer in writing. Anything else is just misinformation.