(Regarding how he got them to reply at all, this is required by law of public authorities.)
The later reply about it being because OCR does use what's below the line and it shouldn't be obscured looks like the ticket was escalated to someone who understood what was really being asked for.
Obligatory xkcd: https://xkcd.com/806/
Evidence in favor of this theory: the "don't write" message is in red text. It's cheaper to do two (or more) passes on one high-volume print run - and then single (B&W) impressions on the smaller runs for each individual letter or form - than it would be to do multiple passes for each and every order.
The support staff wouldn't be privy to these sorts of economic optimizations, so no wonder they couldn't give the guy a comprehensive answer.