The agent likely helped you by taking the B4 that he recognized as "goods to follow" and changing it to B4A. I had a little assistance initially in modifying my B4A and getting copies, and most of my B4A was on a blank piece of standard printer paper, handwritten, with estimated value next to the items.
This doesn't mean one should start putting goods to follow on a B4.
The agent was simply nice, which seems to be a common experience. They are quite anal about forms and following the rules in many circumstances, but in reading other posts and my own experience, they (the CBSA officers at the ground POEs inside the CBSA office) are generally quite helpful during landing regarding the goods forms.