As @tkausl mention in a comment the ::type in the false result branch force it's evaluation:

typename Select_Tag_List<Tag, TagsList...>::type

To fix the issue I added a wrapper around the true branch as:

template<class Type>
struct TypeWrapper
{
    using type = Type;
};

// -----------

using type = typename lazy_conditional_t<tag_index == Tag,
    TypeWrapper<TagList>,
    Select_Tag_List<Tag, TagLists...>
>::type;