For the sake of clarity, I'll summarize the comments above and add a few anecdotes to answer this question:
Bottom line: there does not seem to be any consistency in how a person's residency was recorded in marriage records in late 18th & early 19th century Cornwall.
As per AdrianB38, PolyGeo, and atiras, marriage conventions and Settlement Poor Law were two different entities, and people were more 'fluid' in defining residency when it came to marriage in order to save on fees, avoid others contesting the marriage, etc. Per AdrianB38 and atiras, a person only had to be living in a parish for a few weeks while the banns were read in order for a curate or vicar to consider them 'otp' for recording purposes, and people did lie.
A quick read through the original records of the Parish of Davidstow, Cornwall, illustrates the fact that vicars and curates did make distinctions between otp, sojourner, and naming the specific parish the individual was from, but applied these distinctions rather willy-nilly:
1791: John Uglow & Jenny Chapman; of the Parish of Warbstow, and of this Parish; Wm Laskey, Curate.
1793: Pentacost Parsons & Mary Salter; of this Parish Labourer, of this Parish Spinster; Wm Laskey, Curate.
1795: Wm Fradd & Charity Pearce; Sojourners of this Parish; Wm Pitt Bray, Curate.
1797: William Salter & Phillippa Horril; of the Parish of Forrabury, and of this Parish; Wm Pitt Bray, Curate.
1799: William Broad & Mary Parsons; of this Parish, and Sojourner of this Parish; Lewis Marshall, Vicar.
1807: George Ford & Mary Brechenshire?; of the Parish of Forrabury, and of the Parish of Roach? Lewis Marshall, Vicar.
1809: Richard Mathews, Sojourner of this Parish & Catherine Pearce, of this Parish; Lewis Marshall, Vicar.
1810: William French & Frances Toms; of this Parish, and of this Parish Sojourner; Lewis Marshall, Vicar.
1811: Robert Cory & Alice French; of the Parish of St Juliot, and of this Parish; Lewis Marshall, Vicar.
From: England, Cornwall Parish Registers, 1538-2010," database with images, FamilySearch (https://familysearch.org/ark:/61903/3:1:S3HY-6529-YPH?cc=1769414&wc=3CB8-44W%3A138123201%2C138661201%2C1582884012 : 30 November 2016), Cornwall > Davidstow > Marriage banns, marriages, 1754-1811 > image 16 of 19; Cornwall Records Office, Truro.
In the 1790s, Wm Laskey, Curate of Davidstow recorded that John Uglow was from Warbstow, not just a sojourner, and in 1793 he added the occupations of Pentacost Parson & Mary Salter even though there was no official space for it in the marriage record form.
Curate Wm Pitt Bray recorded Wm Fradd & Charity Pearce as Sojourners of the Parish, and did not record where they were resident according to Poor Law Settlement. But in 1797 he specified that William Salter was from the Parish of Forrabury, marrying a woman 'from this Parish'.
Finally, Vicar Lewis Marshall applies every residence term to different individuals over a span of 12 years. He records both grooms and brides as Sojourners (1799, 1809, 1810, 1811), records the home parish of each (1807), and records both as of the Parish (not shown). It is possible that in Vicar Marshall's mind there was a clear distinction between each of these applications (did Sojourners declare an intent to stay in the parish, whereas those with home parishes listed did not?), or perhaps he just did not ask where the sojourners came from that day.