Generally, currently, ALL adult grant citizenship applicants must attend an interview during which the applicant presents originals of supporting documents.
This was not always the practice, but the exceptions were not related to the test and language exemptions based on being above a specified age (the age exemption has usually been 55+ but for a few years was 65+).
To the extent there may be any current exceptions, the exception is NOT based on the exemption from language and knowledge of Canada requirements for those 55+.
Thus, the anecdotal report that an individual 55+ was not required to attend an interview is almost certainly NOT due to or related to the fact the individual was at least 55 years old, but rather is either a coincidence OR an anomaly (odd stuff sometimes happens).
In any event, the 55+ plus applicant can expect to be scheduled for an interview and required to present originals of supporting documents during the interview and to answer at least a few perfunctory questions, and possibly be subject to more probing questions (if, for example, IRCC has any questions about meeting the qualifying requirements, especially as to physical presence).
