Unlikely that they're trying to get rid of inventory that doesn't sell. If a shop has a decent buying department, they probably will have limited amounts of the very small and very large boots. In my experience, shops are generally short on these unusual sizes.
Additionally, most shops have some sort of boot fit guarantee, so shoving someone in a boot that is far too short only creates a future headache when they come back routinely complaining about their bruised toenails.
In my opinion, the single hardest part about being a bootfitter is sizing up the skier. If I could ski with every single one of my customers before I fit them I would surely have a better idea of what sort of ski boot and fit to put them in. So honestly answering questions a bootfitter asks you is essential. If you tell us you're an expert skier who skis 50+ days a year, we're going to treat you like one.
Believe me, it takes much more time and effort to talk a skier into a boot that fits a little shorter, but if a skier is skiing frequently and agressively enough there are a lot of benefits to a snug boot. If I was lazy I would put everyone in a comfort fit, but again - some experienced skiers would come back with complaints of their feet moving around in the boot.
When doing boot work, we have a lot easier time increasing the amount of space in a ski boot by modifying either the shell or the liner. If a boot skis too big, we can shove all sorts of stuff in it (shims, footbeds, risers, foam, etc.), but chances are it'll still ski big.
For that reason, yes, many bootfitters will favor smaller shells. But, it is generally NOT because we are trying to get rid of inventory. Usually its because we are trying to accomodate the type of skiing you claim to be doing.
However - that does not mean that you'll gain exponential performance from cramming your foot into a boot 2 sizes too small. Your boot may be a tad more responsive - but you'll endure a lot more misery to get it. Generally, we strive to find a happy medium for our customers (and its not always easy).
I don't know where you had this negative boot fitting experience, but I wouldn't go so far as to encourage others to distrust a boot fitter. If you know the person who is fitting you is qualified and you have been honest with them about your ability and experience, I would listen to them, regardless of whether you feel your toe on the front of the boot or not.