Here's my experience. When I went to DriveTest the first time, they said the same thing - that they wont accept the Posting date mentioned on the abstract and it has to read Issue Date. DriveTest told me there is another document from NJ DMV called the Driver Status Inquiry that mentions the original issue date. I called NJ DMV and they said they cannot mention issue or renewal date if it is more than 4 years old. I thought I was never going to receive my Ontario DL.
At this stage, based on Saugaboss' recommendation, I emailed the DriveTest and got a call from them two days later. I told her I have my old expired DL's and current valid DL from NJ going back 5 years and Driver abstract / DL Application Request documents I had brought from NJ DMV before I moved to Ontario. She said they need the Original Issue Date or renewal date mentioned on the documents for greater than 2 years to issue a G license. Then she talked to the Brampton DriveTest and called me back saying she had confirmed with them that I could carry the documents I have and get the Ontario DL. I went there the next Saturday and got it done though there was some confusion at the front desk. The main reason why I got my DL was because of the expired NJ DL's I was carrying (which showed I had more than 5 years of driving experience) and my driver abstract from NJ. Whatever be your case, email DriveTest and let them know your problem and phone number. When they call you, speak politely and explain your situation and I'm sure they will help you. Hope this helps!