I will comply, but I thought they're wrong for regular work trips and this applies only when my employer sends me abroad to work there for a longer period (such as a 6 month installment in another EU country). The formulation on gov.uk, or on the websites of the Finnish or Dutch governments appear to imply it's for cross-border workers more so than for short foreign work trips.
But activpayroll actually does claim that:
Under EU Regulation EC 883/2004, all employees who travel to another EU/EEA country on a business trip must obtain A1 certification. This rule applies not only for secondments of up to 2 years, but for stays of any length, including meetings and workshops lasting only hours, or even refuelling stops in another country.
which comes as quite a surprise to me, because in the dozens of work into other EU countries I've done while living in Sweden or the UK (pre-Brexit), I never heard of such a certificate.
Under what circumstances is an A1 certificate a requirement for employees in one EU country travelling for work to another?