If it's vol as synthetic time, wouldn't the actual passing of time mean the vol ramp is offset by theta decay? If so, wouldn't a pre-earnings straddle (regular or synthetic) be just a long gamma trade with slower time decay?Sure, but more often than not the vol will ramp from say (in GOOGL) 24 to 32 on the penultimate day. The vol as synthetic time. You can't lose on premium with an 8 handle move in vola. It's very hard to lose more than pennies.
Try it with half lots. Cast the net--do a bunch of half-lots and you'll get a feel for how the ticker behaves before reports. Take notes. Model the vol and the pre-report histories.