[tuukkah]

Nobody claims they all speak Finnish well, but the Swedish spoken in Finland is influenced by Finnish and typically includes some loans from Finnish.

[laurent_du]

The person I was answering to literally claims people are bilingual (Swedish + Finnish).

[tuukkah]

Being bilingual is a fuzzy concept: to many, it includes people who speak a language less well, but perhaps enough to get by.

For example, in a bilingual environment, it can be enough to understand two languages and to speak one.