I have had two bikes stolen (or attempted to be stolen). In both cases they threw it in the bed of a pickup truck.
The attempted thieves on one attempt had to be "combatted" to get the bike back.
We also have a neighborhood bike thief where I live today. His trick is to ride a bicycle to where another bike is unsecured, grab the handlebars of an "available bike" where the owner has stepped away, and pedal off with both bikes.
In neither of these circumstances are the thieves relying upon the victim's bike having a chain.
Today, I rely on a good quality lock (Kryptonite), and a WDSCAM tail-light/alarm purchased from Amazon for 36 bucks. If the area is a higher risk area, the bike gets two locks on it, plus the alarm.
When I consider security for a bike, I try to remember most eBikes are a $1000 item (or more). They are a tempting target. The deterrent needs to be at least as strong as the "attraction to steal the bike".