Observations about the timeline between interview and oath:
The timeline range for taking the oath, for successful applicants routinely processed, is huge.
There are probably practical patterns for some local offices. There may appear to be observable patterns for some local offices. Spreadsheet information, however, especially for particular local offices, is way too small a sample, not at all likely to be a representative sample, and subject to sporadic and, frankly, less than credible reporting, and thus is NOT a reliable indicator of anything more illuminating than the very broad range of possible timelines.
Among possible timelines:
Some applicants can be tentatively scheduled for the oath before the day of the test/interview, the oath scheduled to take place the same or next day or within the week or so. Actually taking the oath is, of course, contingent on the outcome of the test and interview. Some of these applicants get notice of the oath in advance (I was scheduled to take the oath the day after the day following my interview, and received notice about ten days before the interview; this is typical in many itinerant services scenarios), while others get notice of the oath at the time of the interview (typically these applicants have the option of taking the oath then, as tentatively scheduled, or later, IRCC allowing such applicants to request a later date if the tentatively scheduled date is NOT convenient, since the notice is so short).
Otherwise, the timeline (again, for successful routinely processed applicants) can range from one month to four or six months, occasionally but NOT usually six to twelve months. Any claims to more definitively assert what the timeline will be for any given applicant are, simply, frankly, NOT trustworthy.
In the meantime, however, unless and until there is a Decision Made for the applicant, it is difficult to know whether the post-test/interview process continues to be routine or becomes non-routine. Obtaining GCMS records via ATIP application will NOT usually divulge if there is non-routine processing taking place. If there is some non-routine processing after the test/interview, that throws the timeline into a totally UNKNOWABLE range, albeit six to twelve months is PROBABLY the likely range.
Many applicants come away from the interview feeling they have been assured all is well and their oath will be scheduled in the routine course. The reliability of such assurances seems to waver some. NONETHELESS, the vast majority of applicants will, indeed, be routinely scheduled for the oath pursuant to the internal practices of the local office.
CAVEAT: Given the huge surge in applications submitted in the last six months, well over a hundred thousand seems quite certain, there will almost certainly be more variations than usual, and bigger deviations. During this period of time, and for most of this year I'd guess, it will be especially difficult if not impossible to forecast how long it is going to take . . . for just about any step in the process . . . for any particular applicant. One or a hundred are likely to go surprisingly quickly. Dozens or hundreds are likely to go much longer, with a sizable percentage of these going a lot, lot longer. With little or no decipherable distinctions, virtually no useful clues for guessing how long it will take any given applicant (other than obvious indicators: those subject to non-routine processing, for example, will likely take quite a lot longer than routinely processed applications).