Hi Khael,

Nice to meet you.

KJ> 1 Pamanna (p. 416) (f.) [abstr. fr. pamana, for
KJ> *pamanya, grd. form. of pa+ma for the usual pameyya]
KJ> only neg. ap╟ immeasurableness Vbh 272 sq. (catasso
KJ> appamannayo, viz. metta, karuna, mudita, upekha). See
KJ> <XREF="APPAMANNA."appamanna.

I consider that it's another myth based on PED, like 'in front of'
rendition of 'parimukha.m'.
Sometimes one should see the glosses and other dictionaries.

Appama~n~naati pamaa.na.m agahetvaa anavasesaphara.navasena
appama~n~naava.

(Pathikavagga-Atthakatha 3.1008)

Appamaa.nanti ida.m tassa tassa phara.na-appamaa.navasena vutta.m.
Ta~nhi cetasaa pharanto sakalameva pharati, na ⌠ayamassa aadi, ida.m
majjhan■ti pamaa.na.m ga.nhaatiiti.

(Pathikavagga-Atthakatha 3.1048)

[Yogin] doesn't take (na ┘ ga.nhaati, agahetvaa) a criterion
(pamaa.na), according to which one goes first (aadi), and another in
the middle (majjha.m). He spreads (pharati) [brahma viharas] on
everyone simultaneously (sakala.m) without remainder (anavasesa),
hence unconditionally.

There's not even a mention of 'immeasurableness'.

Metta, Dimitry