I don't think any of these delays are anything to do with the inspection of the parcels by Customs per se, and more to do with the fact that UPS seems to be in meltdown and seem to be incapable of processing and delivering parcels at the moment. Other courier firms are getting parcels through from the EU absolutely fine, and whilst there is a Covid impact on Border controls I think the situation with UPS is down to UPS. Some of the recent reviews for UPS I've seen online are suggesting a 5-week delay from postage (and ironically most of this time seems to be spent in the UK), which supports the information that @EvilMonkee managed to get that his parcel is currently sat in a container. I suspect there are quite a few GF and TG parcels in there with his, all waiting for someone in UPS to be assigned to them.
Depending on how this all pans out it might be worth giving some feedback to TG and GF and asking them to consider offering alternative couriers, as relying on UPS may well impact their business. I for one will be very wary after this experience. Fingers crossed someone gets their parcel soon, as it'll give everyone an idea as to how long these imports are taking with UPS.