have been teaching for 30+ years...middle school to college.
To me, timing is PART of technique.I encourage metronome use because part of the physical act of drumming - the stroke, rebound, grip pressure etc - is also how your brain moves all of that around space, and how the division of that space via pulse effects how you use all of the physical stuff.
When I start my beginners, we are totally focused on the physical...while the met is going "in the background". I start all of my students with the classic 8 on a hand from marching band. To me, that is like "long tones" for drummers.
As they get better at manipulating the physical, then I start moving them to the next level of space control. This is usually 2 months (given how much they practice at home) in to the lessons. This is where we start testing the hand technique by talking about timing technique, and hoe the addition or subtraction of space effects how you use your hand muscles to play in that space. Their use and analyzation with the met starts to grow here ,and they become comfortable with how and why we use the met.
I ALWAYS encourage analyzing with the met...and eventually, learning with it on. But they have to develop the "learning patterns" skills separately first. As someone mentioned, it is pointless to use a met on patterns that your hands don't know yet. By the time they are a year in, most of my students (again, who do the right thing at home) can learn with the met going, and understand how to use it.
I think that shunning, or even discouraging the use of the met is just as shortsighted as shunning rock for jazz, or marimba for drum set, or traditional for matched...and really, since learning time is a learned thing ( I don't believe it is automatic), not using them met is counter productive...especially at the early stages where your brain is imprinting concepts.
The metronome is a defining tool...like a ruler, because it defines space. I am pretty sure that many architects can "eyeball" space, but the good ones use a ruler when actually defining space in their art....we should too...