Not shocked, at all.
Those tips aren't any smaller, really, except for the knife tip. You can get all of the others in the better thermal performance T18. Conicals, bevels, and chisels, all just as small as the 900S. For really fine work, under a microscope, all you are going to see is the very tip of the iron, anyhow. Not the width/diameter of the barrel/base, which is going to be miles away from the action.
Many of the clone 900M handles have poor thermal performance, putting a lot of heat into the handle. I don't think they are going to have much luck getting a 900S pencil to work adequately without melting, using the same cheap materials.
Good luck finding your pencil, though. If you want short tip to grip, then consider buying cheap T12 clone, maybe. Or in the EU, you can get an Ersa? But "smaller tip" you don't need to do anything but order the right one for the 936. They go just as small.