Does the "Rule of 15" suggest that you should pass with 13 points (and short spades) in fourth seat?

Question

Only you vulnerable, you have a 13- high card point hand like the following: (s)x (h) AJxx (d) KJxx (c) KJxx. (No x is higher than a 7). Three passes have preceded you.

The "Rule of 15" suggests that you open in fourth seat only if the sum of your high card points and spades add up to at least 15. It works most often for 11 point hands with four spades. Here, you have the full opening point count (13), but are weak in spades, the highest ranking suit.

On "average," your partner will have nine, or one third of the remaining 27 points, giving your side about 22 (out of forty). Balanced against this is the near-certainty that the opponents own the spade suit. (Partner would have opened with a "weak two" spades with six, unless they were very weak.)

Does this consideration suggest that you should pass in fourth seat, even though you might have opened, say one diamond, in first, second, or third seat?

Edit: I am now also assuming unfavorable vulnerability, that is "only you vulnerable" (the original version of the question said both vulnerable). Does vulnerability make a difference in this borderline case?

Answer 1

Rule of 13 trumps Rule of 15.

If you have 13 points you open.

If you read the first few sentences of the article you linked, it says clearly you only apply that when you have 9-12 points.

Answer 2

Larry Cohen here explicitly provides, as an example of failing the Rule of Fifteen, this eleven point hand:

S: 3
H: K J 5 4
D: K J 8 7
C: K 9 8 7

However, he proposes the CRIFS variant - Cohen's Rule in Fourth Seat - Whenever the Pearson Points count (HCP + # of Spades) is between 14 and 16, instead assess your opponents. If they are amongst the better players of your club pass, and if they are amongst the weaker players of your club bid. To quote Cohen directly:

Who needs to open and have to do battle with an expert pair who will fight hard for the partscore and play or defend well?

Update

In regards *vulnerability, I see that as irrelevant at this decision point. The amount by which one goes plus or minus instead of taking a zero score is of much less significance than assessing the relative likelihood of each.