You have a good memory! As you know per the fine print of the sellers/manufacturers, you have to shift every piece of furniture in every room on a frequent basis and vacuum etc under that. By their own admission, the treatment does not stop the fibres from disappearing - in other words, their pre-treatment does not work.
Edit and update of my own anecdote. Separate renovation on another part of the property with synthetic carpet - zero issues. Ongoing treatment and vacuuming etc with infected areas has made zero difference - in some cases the carpet is now threadbare.