Considering a setup where default and fallback locale are configured differently (e.g. default (unsuffixed) locale is German, fallback locale is English):

When current locale is German, AbstractI18nContentSupport#getProperty() first tries to resolve "property_de" (note the suffix)
— because that doesn't exist, it keeps looking up for the next locale, down to the fallback one, that is English.

Whenever current locale is the default locale, it should also try to lookup the property un-suffixed.