Need help in clarifying techniques used in isolating bacteria

Hi,

I do not have sufficient background knowledge in environmental microbiology and I am reading several research article about this. The topics are generally about isolation and screening of microorganisms used for bioremediation of (micro)plastics.

I noticed a very tiny difference between each paper.

All the papers start like this:
1. Sampling of contaminated soil (some are from mangrove sites)
2. Mixing x gram of this soil in x mL of water or saline water

The difference is that some papers cultured that mixture from (2) straight into enriched media with the specific contaminants (Method A).
Yet, another papers cultured that mixture from (2) into general media (NA plate), isolated the microbes, and subcultured them into NA again. Only after doing that, they isolated the subcultured microbes into enriched media with a specific contaminants (Method B).

So what are the differences between A and B? Why do the long procedure (method B) if you can culture it directly in an enriched media? Are there any advantages of doing B instead of A?

Thank you in advance for answering my questions.