A fact which renders these trackers completely useless as anti-theft devices
Not really, even if a thief is alerted something is being tracked if they can't find the tracker they will throw out the object they stole... which you can then recover. and also potentially get video evidence from around where it was dumped to ID the thief if they still have something from your backpack...
I have a hidden compartment in my backpack where I often put cash so I very much would be happy to recover even just the empty backpack without contents.
Or if you had an AirTag hidden in a car they might just ditch the car rather than take it to a chop shop, and you can at least find where it was ditched.
Also did you forget "unintentional theft" exists, where for example an airline rather than flying your bags to your destination, takes them elsewhere... and when that happens sometimes they have no clue where the bags are. If you have a tracker, you can tell them what city and facility your bags are in, and even play a sound to help locate them.
AirTags (and the new Android form) are incredibly useful even with tracking detection abilities, you are really missing out on this super cheap insurance and recovery aid.