[netheril96]

I am a complete noob regarding SEO. My naive interpretation of the drop in rating is that it takes time for Google to rebuild the index. It needs not only the content on your website, but links from other websites and people's clicking habit to determine the ranking.

On what level is my interpretation wrong?

[spacecowboy_lon]

not any more back in the day (several years ago) it used to take time for google to index a site

[mtbcoder]

I think he's referring to domain authority (PageRank) and not just indexing. GoogleBot can hit your site several times a day and index things quickly. Building your domain authority on the other hand and connecting all the dots (like your back-link profile) takes a long time.

[blumkvist]

Google treats subdomains (almost) like completely different sites. Links to the root domain do not count for the subdomain and vice versa.

[TeMPOraL]

AFAIK it treats some common subdomains (e.g. "blog.") as part of the main site.