If shinki had an appearance in that story about giving her the pajama's or any of the gifts for that matter was hinted or mentioned it might have a slimmer of hope of being connected story wise, but whats really being done is something small and irrelevant has been introduced to "advertise" another work. I think you're looking into it more than necessary.
Trying to put a timetable to these works isn't possible with the references they make to other works alone, like nezchan said, it's just a running gag he uses.
Edit:The examples I used aren't exact, but they are real examples of references made from one work to another, that doesn't make them sequel worthy either.
last edited at Nov 3, 2015 9:20PM