Yeah, it is fully possible I threw in more than one pero pudding or some such, which would bump it to the next tier from my original estimation. If I ever get the materials again I will give it another shot to at least see if I get silver.

In fact I will see if I can just load up one of my other accounts and quickly test it.

Edit ↓
Tried with two R gacha tickets (supposedly 1300) and got silver (with a wait time of 60 minutes). Candyx20 + wild card 3. That about matches up with most of the silvers I remember getting.

Maybe it is the case that <1500 is not a guaranteed silver? Or the 780-1500 not being silver might be inaccurate for our version at the moment. Either way, guess that only shows it is possible to get silver rewards at <1500 and not necessarily that the SR can drop there.