[necovek]

What everyone else is saying is that the core value proposition of microservices is that they are independently deployable (which I believe is what you are aiming for as well), which means that there is no tight coupling between them.

If one introduces tight coupling by having a shared library that gets updated in backwards incompatible way and needs to be updated simultaneously in each microservice, you move away from a microservices architecture as your services are not independently deployable anymore.

So in the general case, it is immaterial, but in practice, it can be a mechanism which introduces tight coupling and negates the core value of the microservices architecture.

Here, it was done on purpose as a step to a more monolithic architecture (though it was still only a single service in a larger system, so I'd avoid the "monolith" term).