Becquerel (or counts per second) have the same problem in that they don't measure the "energy" of each request.

I do like the analogy though. Actual radiation has many forms and energy levels.

Decay chains are a nice analogy you could use too (i.e. a branching out of subsequent processes and work that come later, but are a consequence of the initial request).

And yes, like Sieverts, some types of incoming request, and some "organs" are more consequential than others. There's even an analogy to "committed dose" as the database accumulates things.