You asked a question, and I politely answered it. The rest is on you.
Queuing at a bank branch has a cost of some sort (compared to unit trust-ing it from a sofa), and there’s a slight risk the T-bill could straddle one or more months when SA dollars would’ve earned interest above the floor rate. (With a unit trust you’re in and out when you know what the SA rate is. We don’t know the SA rate yet for 2Q2023 and particularly 3Q2023.) In my view 4.00% EIR is clearly too low for a T-bill but 4.66% EIR is clearly too high. The answer for me is somewhere in between. So (finger in the wind…) I’ll accept the halfway mark, thanks, to reflect the queuing cost and SA rate risk. You don’t like this answer, but it happens to be a reasonable one.
What EIR would like to suggest as “the“ answer? You want to argue it’s actually 4.26% EIR that tips the balance in favor of T-bill-based shielding instead of unit trust-based shielding? Or 4.37% EIR? Or something else?

If you want to compute the cost of bank queuing based on wage rates and then add in some formula about SA interest rate risk over the T-bill tenor, be my guest and have fun. But I’m very comfortable with 4.33% EIR if I were making this decision today or soon. It’s “close enough,” and that’s all that’s required here since queuing costs and SA rate risks are hard to quantify.
OA is different. Different scenario, different estimates. And no, I would not queue in a bank branch for mere breakeven. Less rate risk, too. (SA will unpeg from floor way before OA does.)