This is a list of examples of nouns in -tio which are not formed from known verbs, together with certain ancillary information. I have tried to be exhaustive, but perhaps other examples will be found. Corrigenda or further examples are appreciated.
prefixation with in- of a noun in -tio deriving from a verb:
immoderatus and immoderatio but not *immodero
imperfectus and imperfectio but not *imperficio
inordinatus and inordinatio but not *inordino ;
ineruditus and ineruditio but not *inerudio ;
incorruptus and incorruptio but not *incorrumpo ;
other prefixation of a noun in -tio deriving from a verb:
praedispositus and praedispositio but not *praedispono ;
cognatus and cognatio but not *cognascor;
derivation from a substantive with an implied first conjugation verb in -o (usually, sense: provided with):
racemus and racematio but not *racemo;
pampinatus and pampinatio but not *pampino (verb);
tabulatus and tabulatio but not *tabulo (however: contabulo, deriving somewhat oddly as con- + tabula + -o).
exotic construction:
graduatus and graduatio but not *gradio (however: gradior/gressum).
Overall, several things can be noted:
1: a mid double-digit percentage of commonly used verbs form nouns in -tio;
2: of the nouns in -tio, well more than 99% are formed from an existing verb;
3: of the exceptions:
3a: 75% of Aureate usages are explained by implied verbs of possession (racemus -> *racemo -> racematus -> racematio)
3b: 75% of religious usages are explained by prefixation of existing substantives in -tio with in-
3c: there is one Aureate example of the mostly religious usage: immoderatio
3d: also Tertullian introduces a word according to the older pattern: racematio
3e: Francis Bacon had new ideas and apparently needed new morphology
It is worth noting that all of the in- prefixed exceptions mean `not': immoderatio is immoderation; imperfectio is imperfection; inordinatio is disorder; ineruditio is ignorance (and a double negative). It is unlikely to me that in any natural Latin morphology, including natural Ecclesiastical usages, incorruptio by its morphology means incorruptibility.
I still think that this is a calculated poetic use of the language by St Jerome. I regret, however, that I find myself making a textual argument for a linguistic problem; I realise advocating for exceptions is not really desirable until everything else has been exhausted. I regret also for the long note; but I felt as much of a statistical argument as could be made required an attempt at exhaustiveness to constitute an attempt at validity.