Working day length effects use of elapsed time

I am managing a sheet where we use a combination of working days and elapsed days for different tasks. I am noticing some odd behavior using e-days where using an e-day causes the end date to shift an extra day, even if the task falls totally within working days.

In this test sheet I create a task that takes 2 days and starts on Jan 23, 2024. The end date auto-populates to end on Jan 24, 2024 as expected:

However, when I change the duration to e2d, the end date shifts to Jan 25, 2024, even though Jan 23 and 24 are both working days:

From my understanding, changing the above to e2d should not change the end date, as it is not skipping over any non-working days.

I've realized that something is going on related to the length of a working day. Currently, the sheet is defaulted to 8 hour working day and I see this unexpected behavior. However, if I change the length of a working day to >12 hours, I get the intended result. Below, I only changed the length of day to 13 hours:

Based on the above situation, I have 2 questions. First, can someone help explain to me what's going on here? And second, is my solution to changing the workday to >12 hours effective in this situation? I don't want to be introducing unintended consequences to other entries in the sheet. Note that we are not tracking hours or partial days in this sheet, I just need the dates to line up as I'm expecting

Thank you!