Follow-up for potentially too few clusters from VPDigits

The following discussion from !626 (merged) should be addressed:

• @hcroft started a discussion: (+1 comment)

  @tlatham @edelucia It looked like it works OK. The detdesc and dd4hep outputs for Boole.boole-VP are the same. I do want to check somethings though, in the 10 events run from root://eoslhcb.cern.ch//eos/lhcb/cern-swtest/lhcb/swtest/boole_integration_run3/MC_2024_SIM/00230945_00000107_1.sim there are 2557 Signal VPDigits (and 6782 out of time VPDigits and zero noise) but that gives only 322 clusters in total, that does not seem like enough. I try and check this asap as it looks wrong, but it could be OK and I'm reading the log wrong.

cc: @zexu, @mexu