I suppose one could presume there is no SMT in the M1, but I would prefer seeing a definitive statement.
There's no mention of SMT in Apple's documentation for M1. The closest we can get to definitive is what macOS tells us.
- On a Mac with an Intel chip supporting Hyper-Threading Technology, Activity Monitor → Window → CPU Usage shows twice the number of vertical bars as System Information → Hardware → Total Number of Cores reports.
- On a Mac with an M1 chip, the number of bars is the same as the number of reported cores.
Therefore we can conclude there is no hyper-threading.