....which is why the 1N4148 was used in the 'variant 2' circuit ! See posts #19 and #20.
Simulation doesn't show any evidence of junction breakdown. Even if there were breakdown, the base-emitter junction reverse current would be limited by the 10k resistor to a harmless (to the pnp) level and its effect at worst, IMHO, would only be to increase the cap discharge rate (hence reduce the alarm hold-off time) if reverse collector current flowed while the emitter was below ~ 4V.