It gets fairly chilly here in the winter months, and out of the diesels I have owned: 2001 6.6, 2016 Colorado 2.8, and 2020 Silverado 3.0, I would say none of them (when properly running) ever required the block heater to start the engine. The 2001 had a time when only one glow plug was working, and that stint did require the block heater to compensate in the cold. On the coldest of nights I do sometimes plug in just in case, and it feels like it is a more graceful start when I do. I plug in before i go to bed - 8pm-10pm, and start up around 4am, so it stays plugged in for 6-8 hours.
For the current tractor JD 3039R, i always plug in if i leave it out overnight, or for the entire day - no idea whether it is necessary or not. My old JD 770 did not have a block heater, so I relied on glow plugs only, and I did have one time where stored in a not quite weather tight un-insulated garage, and it did not want to start and run on all 3 cylinders.