This is 100% accurate and not to be taken lightly. They have what is known as the "Undesirables Law". If you have a criminal record of most any kind you have to go through extra steps to get that cleared before you will be allowed entry. This got very tightly controlled after 9/11 primarily at the road crossings. Flying in is easier.
I lived in Buffalo for six years in the late 70s and 80s and crossing into Canada was very easy. A few questions, maybe show a drivers license, etc. Now it is not and if they pull you over for more questions they have access to a lot of U.S. information.
I used to lead fishing groups into Canada to fish the un-colonized areas of northern Quebec. Prior to 9/11 no problem getting everyone across the border. After 9/11 the Canadian customs would pull us over if it looked like we were sportsmen and if anyone had a DUI they were denied access and one vehicle had to turn back. Other kinds of criminal records had different consequences. At first, I stopped travelling in groups and finally I just stopped doing these group fishing trips.