The tests related to ClassificationNeuralNetwork are extremely slow compared to the others on Debian x86-64 CI runners.

See for example those logs which have timings prepended to each log line:
https://ci.debian.net/packages/o/octave-statistics/unstable/amd64/56397827/
https://ci.debian.net/packages/o/octave-statistics/unstable/amd64/55938923/

This leads to timeouts on the CI runners.

Curiously, the problem does not manifest on other processor architectures (not even on x86-32).

Do you have any idea of what might be causing the problem?