Valid point. DP3T (in one configuration) adresses this and lets you filter out certain parts that you do not wish to disclose. Thus, this then requires you to upload all broadcast identities used in the relevant timeframe, but because of space-related issues is then „compressed“ using a Cuckoo-Filter. This, however, yields false-positives. To eliminate those to a managable amount, it further requires more space.

So, this has a tradeoff. Personally I don‘t think that linking multiple IDs in a day is a big intrusion of your privacy (and remember, it‘s only disclosed to anyone for the timeframe that is epidemologically relevant) - full de-anonymization still requires some second channel, such as cameras or the like - which can be linked together without those Broadcast IDs anyways.