Kacc 1-5-1 (query & translation)

Re: 1-5-1

OPS §38: "…[This verse] states that 'in some cases the final a of
putha gets the augment g before a vowel.' The vutti quotes the example
puthag eva which is recorded neither in the canon nor in the
Aṭṭhakathās. It is difficult to believe, however, that Kacc describes
occurrences that are not instantiated."

I have found one instance in an e-text of the Abhidhammatthasaɲgaha,
p. 248, as follows: ārammaṇantarehi amisso puthageva koci upanissayoti
vuttaŋ hoti.  It also appears in the neo-Pali work Jinavaŋsadīpaŋ (p.
502), which is, no doubt, a product of the rule above rather than
truly instantiating it, as with its appearances in later grammatical
works.

Here's my current translation of the verse (subject to change):

{Sutta:} Putha sometimes [takes on] g as an augment [where followed by] a vowel.
{Vutti:} In the same way [as the foregoing rules], where the ending of
putha [stands] opposite a vowel, [it] sometimes [takes on the] the
letter g as a euphonic augment.
{Note:} [This rule is addressed to the adjective puthu where it forms
the first part of a compound and ends with an -a.  From the
perspective of the Pali language, the word is puthu (and will be found
spelled as such in the dictionaries), not putha; however, both here
and in the eighth verse of this chapter, it is evident that the
author(s) of the verse thought of this word in terms of its Vedic
etymology, viz., the roots pṛthag and pṛthu (cf. 1-5-8, with which
this verse is reciprocal).]
{e.g.} [Thus, puthu + eva may very rarely result in:] Puthageva.
{Note:} [Or, with reference to its etymology, the example may be
explained as pṛthag + eva = puthageva; it is not entirely rare for
euphonic augments to restore archaic features that had dropped out of
the language in the period of the canon's compilation.  However, the
particular instance described by this rule is so rare that OPS §38
suggests it does not exist (cf. notes to the Pali text).]
Why only "sometimes"? [Because the rule is not absolute, and so the
same example may be written:] putha eva.