Song of Creation does not give mana to cards drawn outside of the cast trigger.
Also, it doesn’t give mana when vanguards are cast. I just retested it to make sure. There was no mana given or card drawn after casting Tamiyo vanguard.
Edit-
Regarding FindingHeart8’s post, It does give mana when using Tamiyo’s ult, but I have also noticed inconsistencies with other draw effects not triggering it.
Yes, I have seen this a lot
Anyone else had the opponent’s SoC trigger when you cast lands on your own turn?
Pretty sure I had a game where Tamiyo‘s SoC was triggering its Resourceful effect when my lands went into play. Drawn cards and mana to SoC’s owner.
But, I have not had another ideal match to test it again.
@FindingHeart8
Could you provide your deck or any key cards you think helped triggering this issue?
It would help a lot with the investigation.
Also, the SoC + Vanguard issue is already fixed for the next release.
Yeah, for starters it doesn’t work when you activate the 2nd ability on Bolas1 (Amonkhet), or B/G Garruk (Eldraine), both abilities involve card draw that should trigger SoG’s mana ability.