IANAL, but I've spent plenty of time with government processes and rules, so here goes my take FWIW.
The regulation in question:
(a) Except for work performed in accordance with ??91.411 and 91.413, each registered owner or operator shall keep the following records for the periods specified in paragraph (b) of this section:
(1) Records of the maintenance, preventive maintenance, and alteration and records of the 100-hour, annual, progressive, and other required or approved inspections, as appropriate, for each aircraft (including the airframe) and each engine, propeller, rotor, and appliance of an aircraft. The records must include?
(i) A description (or reference to data acceptable to the Administrator) of the work performed; and
(ii) The date of completion of the work performed; and
(iii) The signature, and certificate number of the person approving the aircraft for return to service.
In a nutshell, the debate is over this set of clauses:
"Records of the maintenance, preventive maintenance, and alteration and records of the 100-hour, annual, progressive, and other required or approved inspections, as appropriate, for each aircraft ..."
In simple English, this is two active clauses, one concerning *maintenance*, and the other concerning *inspections*.
"Records of the maintenance, preventive maintenance, and alteration
and
Records of the 100-hour, annual, progressive, and other required or approved inspections, as appropriate..."
The first clause is not restricted by the "as appropriate" modifier. Thus, it would, it appears, apply uniformly. And I think that makes sense...maintenance, preventive maintenance and "alteration" (whatever that means) gets logged.
The second clause applies to *inspections*...100-hour, annual, whatever is appropriate for the aircraft (i.e., 100-hour inspections have nothing to do with type certificates...that's dependent upon whether the aircraft is used for hire). If 100-hours are not appropriate because the plane is not used for hire, then clearly, there's no need to log it.
*I* would have written this as two separate requirements, but that's because in my line of work, such compound requirements are, uh, bad...see the confusion they lead to?