Is it a mapping or rendering problem? I checked on OSM, and it seems weird tagging to me, but I’m not sure how people map airports in Germany, so hence this topic.
I only had a quick look on my phone. It seems that most of the terminals should actually be tagged as gates (aeroway=gate). But I had to check this again in detail against the official airport map. As far as I know, there are only two terminals in Frankfurt.
But gates are usually the single gates “A20” etc. (aeroway=gate) while “A” is the concourse and “Terminal 1” is the terminal (aeroway=terminal). It looks to me like there is gap in the OSM tags for aeroway=concourse.
Gates sind doch normalerweise einzelne Flugsteige “A20” etc. (aeroway=gate) während “A” den Fluggastbereich und “Terminal 1” das Terminal (aeroway=terminal) ist. Es sieht für mich etwas so aus als fehlt einfach ein wirklich passender OSM-Tag dazwischen wie zum Beispiel aeroway=concourse.
I agree with @yannikbloscheck , it seems there is a lack of a formal concourse tag.
It seems there is some uses of aeroway=concourse, (aeroway=concourse | Tags | OpenStreetMap Taginfo). I don’t think keeping as terminal seems a good practice, so perhaps it’s better to switch to this tag, even though it’s not official nor supported anywhere (yet)?
There are a lot of MP-relations and building, which in my understanding should be rather building:part and several are tagged with aeroway=terminal resulting in the mess.
There are at the moment Terminal 1, Terminal 2 and the LH FirstClass Terminal, in 6 months also Terminal 3. I might take a deeper look on the weekend and try on cleaning up, but you can go ahead…
In general it seems to be best practice to tag the concourse as aeroway=terminal, checked now on several mayor airports globally. So I would think that part of the discussion should be held in the General Tagging section. I tend to agree with you, but it also should be similar globally.