Quick answer to these cases Pihlajaniementie & Patorannantie :  these roads cross the municipality border going from a primary Finnish municipality to primary Swedish. The signs seem to be on the "Finnish side". Therefore I think we should switch the language prioritization for the roads in the different parts of the roads. So they should be splitted were municipality the border is crossed. The last example (Harjunpääntie) is exactly from this former Pohja municipality. So either the Google picture you're refering to (note shouldn't be used as reference in OSM) is either very old or the municipality hasn't had time to update new municipality language "settings".