Unfortunately even that isn't clear-cut. For example, the WD60EFAX (6TB) Red drive is SMR, but the WD80EFAX (8TB) and WD101EFAX (10TB) Red drives are (at present) not.

Bear in mind that WD have historically made significant changes to drives without updating the the model number at all -- for example, in an earlier iteration of WD Red 2TB drives, you could buy a WD20EFRX with either three platters (slower, heavier, hotter) or two platters (faster, lighter, cooler), with no way to determine which you had externally other than by weighing it. Hopefully the negative press coverage will discourage them from doing the same with SMR drives...

The best resource I've found so far to help determine is The HDD Platter Capacity Database, which lists the platters used in various models, and indicates whether they're likely to use SMR. But even that may not be 100% accurate and complete.