If you placed the ALT file in the scenery folder it wouldn't work, it is an entirely different beast to the other files and the method was developed by the ADE team to overcome FSX loading default ALT files before it loaded up the addon scenery folder, thus rendering any new ATL adjustments invalid, having them in the scenery/world/scenery folder means they get loaded first and thus over ride the default settings.
However, the scenery I made for the strips does not have a default alt setting (a fact I came to realise later) and thus I am pretty certain that even if you deleted your ALT files associated with any of the PF sceneries you would not notice any difference. It was necessary during the building of these strips to change the alt a few times as it is pretty much guesswork trying to get them to blend in well and a few times the guess was out, so a new alt had to be sewt, this automatically generates a new ALT file, which I duly sent out, BUT! as there was no default strip there in the first place there was nothing to "beat to the door" so to speak, the alt change in the ADEX files (.bgl & .cvx)works well enough as they are the only files for the place. On the other hand the ALT files supplied so far do no harm as such, so rather than make a song and dance I just left things as they were with the remaining sceneries to come that used them, having them deleted.
Hopefully this will make clear exactly what the ALT files are all about and the role they play (or not as the case may be!)