dddd

It's more than just the hardness of the metal, it's also the sharpness and especially the angle of the teeth and the pressure applied that determines if the blade begins to cut into the surface at all.

My experience here tells me that these blades tend not to cut into the steel at all, even after my having sharpened a few of the leading teeth near the tip on previous such efforts on frames made from mere Cr-Mo tubing as used on mid-range mountain bikes.

The teeth on a file are configured to cut into a steel surface with little pressure applied, but these blades would require a LOT of force applied for cutting into the inside of a steel tube to occur at all. I did apply significant force of perhaps ten pounds, and yet when I probed the inside of the tube after pulling out the post stub there was no groove or steps cut into the surface!

I do still recommend doing as I did here, periodically running a bottle brush into the tube, inspecting with a bright headlight and probing the groove for aluminum (versus slick steel) with the sharpened spoke that I bent 90-degrees near the tip. The spoke was also helpful initially for determining exactly how far down that the end of the post was.
I also applied oil to the blade every 30-40 seconds of cutting so as not to clog the teeth with aluminum.

Don't use wood blades for this, at least not the pruning blades. Those have teeth with alternating left-right teeth that don't grab the aluminum in such a way as to give you feedback (tending to pull the tool into the seat tube) that the blade is cutting aluminum. Again, even the demolition (wood/metal) blades don't grab the steel that way at all.
So the whole process took about 15-20 minutes.