4-level stack manipulation on 12c

[jemin]

I have an issue related to the "stack lift" on hp12cp CNA02107739.

The p 230 of the manual says:

"When a number is entered into the displayed X-register — either from the
keyboard, from a storage register (using RCL), or from the LAST X register (using LSTx) — the stack usually lifts first. The stack does not lift if the last key pressed before a number is entered was one of the following: ENTER, CLx, ∑+ or ∑-. If one of these keys was the last key pressed, the number in the displayed X-register is replaced when a new number is entered."

However, the following happens when using LASTx:
1 ENTER
2 ENTER
3 ENTER
4 %

The answer at this point is 0.12 displayed and the following is in the stack:
T 1
Z 2
Y 3
X 0.12
L 4

Now, if we follow the manual above, hitting CLx and immediately g LSTx should replace X 0.12 with L 4 without lifting the stack. This does not happen. Instead, CLx sets X to 0, lifts the stack, LSTx then changes X to 4. The result is the following:

Expected Actual
T 1 2
Z 2 3
Y 3 0
X 4 4

A bug or a feature?