I lean towards genuine, as I said in that lengthy post. What makes you think they "often" printed dials in house? They were probably missing the specialist gear like a dial press so would have been reliant on suppliers for blanks anyway - would surprise me if they didn't hand over printing duties to companies like Singer in that case, as they were more geared for it. Maybe some prototype dials were hand-finished in house but dial design seems to have been a collaborative effort back then. Take a look at the similarity of register numerals across many companies in the 60s and you see the suppliers could even dictate what the watch companies would get to an extent. I'm sure Rolex paid well to get the distinctive numerals on the Newman Daytonas to get those distinctive numerals.

I'd be surprised if any series production dials got anything more than a final refinishing touch at Heuer.