Precis exakt såhär står det enligt din länk
Airport transit (non-Schengen travels)
Changing flights without leaving the international transit area of an airport does not constitute an entry into Germany for the purposes of the relevant regulation (Einreiseverordnung). In these cases the digital entry registration, requirements for mandatory testing or providing proof of vaccination, quarantine regulations and travel bans from countries affected by coronavirus variants do not apply. This only affects travels from a destination outside the Schengen area and with a destination outside Schengen area – for example from Moscow (outside Schengen) via Frankfurt (transit) to Buenos Aires (outside Schengen).
Alltså, beroende på destination kanske det krävs.. verkar ganska solklart @Hachans?
Och så läser vi igen. Ovanstående gäller enbart vid transfer non-schengen till non-schengen. Inget annat. Från Tysklands regering sida. Sen har Lufthansa andra regler, de står på Lufthansas sida.