There are plenty of pages about how to add the symbol, and I even found a Stack Exchange Engineering post about what the difference between a dowel pin hole and a regular hole is (unanswered, naturally), but no definitive proof that this is anything other than a convention. I only found two references to standards. The first is this thread
https://www.eng-tips.com/viewthread.cfm?qid=135587 which fingers ASME Y14.100, but if there is a reference to it in Y14.100-2017, I can't find it. The second is the title of this video:
https://youtu.be/-g-nbfJJHps which alleges that it's part of ASME Y14.5-2009, but that standard doesn't mention a special dowel pin symbol. That video does have one useful comment however:
Paul Beaudoin
2 months ago
This Dowel Pin Symbol is NOT an approved ASME drafting symbol. I've scoured every page of ASME Y14.5-2009. There is NOTHING mentioned about this symbol. This Dowel Pin Symbol is used by the Aerospace Industry ONLY. NO OTHER INDUSTRY. Because of the large airplane parts requires such a small scales (1:100 for example) to fit onto standard engineering paper sizes, the dowel pin holes appear as microscopic dots, hence the reason for the symbol. NO OTHER USAGE OF THIS SYMBOL IS REQUIRED. Someone please try and prove me wrong and quote me a page number of an ASME or ANSI standard that shows this symbol as "official".
So it's not from a standard at all, it's just a convention.