Terpe is right, even though the EU Supreme Court ruled (late March, early April of this year?) that 3 months of actual and genuine stay in an other member state is sufficient. This was in a case versus the Netherlands though. UKVI should know better but, as seen around the EU, being tough on immigration - including spouses or unmarried partners of citizens - gets administrations into office...

I am a fan of the EU though, without it there wouldn't be an SS route since there would not be freedom of movement. When it was drafted, immigration and visa rules for country nationals were lighter, and these EU rules were thus less tolerant or kind. Since then, most countries tightened up the rules and now national rules are often more strict then those that apply to EU citizens! Sadly, such discrimination against citizens in their own country is allowed, probably because nobody ever thought that the less tolerant EU rights would, one day, actually become less strict then national laws. My two cents: If a couple is not bothering anyone (no leaching of the welfare system, not being like a unintegrated chav scum etc.) who are we then to deny them entry to our countries?

UKVI knows better, but I'll bet they are going to give people who return after just a few (3-6) months, a hell of a hard time! Probably will take a few years for UKVI to be corrected by the EU Court...