What regulations or policies address rescheduling of Reserve training?

AR 140-1
3-12. Rescheduled training (RST)
RST will enhance the ability of the unit to perform its assigned mission. Commanders should use the RST to increase
flexibility in scheduling training activities that directly affect the unit's training status. Commanders will ensure the
RST is not abused and that the soldier or subsection performing the RST is contributing directly to the unit's mission.
Such training should be accomplished by complete subordinate elements of the unit, i.e. team, section, squad, platoon,
or composite group as directed by the commander, whenever possible. The period of training for the RST will be of the
same duration as that scheduled for the UTA/MUTA.
a. All RSTs must be approved before the UTA or MUTA for which it is substituted. All participants must be
identified by name or by their subsections in the approving document.
b. Commanders will use RST when they feel a training activity is better accomplished at a time, date, and/or
location other than the scheduled UTA/MUTA. The training activities may be scheduled for subsections of the unit or
for individual soldiers. RST initiated by the commander for soldiers or subsections will be annotated on the training
schedule and will be the approving document.
c. Individual soldiers or section leaders may request an RST if there is a training activity that is better accomplished
at a time, date, and/or location other than the UTA/MUTA. Individual and subsection requests for RST when approved
by the commander will be annotated on the training schedule.
d. All RST schedules will be attached to the monthly training schedule, per paragraph 3-1. All participants must be
identified by name or subsection. A training schedule must be prepared for each RST period. An RST window consists
of all RSTs scheduled within 30 consecutive days that includes the assembly (UTA/MUTA) date. The first RST
scheduled to be performed before the UTA/MUTA will begin the RST window for the unit. If no RSTs are scheduled
before the UTA/MUTA involved, the UTA/MUTA date will begin the RST window.
e. RST will not be granted for the following situations:
(1) Convenience of the soldier. However, employment conflicts, overtime, schooling, loss of income, verified
medical problems or personal emergencies, may in the judgment of the unit commander, justify RST authorization.
(Note: When circumstances preclude use of the RST option, AR 135-91, para 4-7b will apply.)
(2) Attendance at conventions or seminars, professional conferences, trade association meetings, or similar gatherings. (This applies unless it meets the criteria of para 3-29.)
(3) If it would cause the soldier to exceed 48 paid assemblies in a fiscal year.
f. RST will be scheduled for soldiers who miss a UTA or MUTA because of scheduled AT. This is the 14-day
period of training prescribed by section 270(a)(1), title 10, United States Code (10 USC 10147). Assemblies must be
scheduled within 60 days of the UTA or MUTA that conflicts with the AT date(s) for each soldier so affected. RSTs
performed per this paragraph will be credited in the attendance percentage for the RST window under which they fall.
g. RST may be granted to ROTC SMP participants to attend certain school functions that, in the judgment of the
commander, would enhance their military training and professional development. Such functions must meet the 4-hour
rule, be performed in the prescribed uniform, and be documented on a DA Form 1380 signed by the PMS.
h. Soldiers are entitled to pay and retirement points for duty performed under the RST training schedule. Both
performance and nonperformance of RST must be reported on DA Form 1379 per AR 140-185.

I am not current (retired in 06), but the following might help you. Read #4 a couple times.
https://www.armywriter.com/memorandum-RST.htm

Also check into AR 140-1 You can download of the net.

The favorable actions suspended by a flag are listed in ch 3-1 of AR 600-8-2.
RST, SUTA and authorized absence are not listed as favorable actions.
https://armypubs.army.mil/epubs/DR_pubs/DR_a/ARN30769-AR_600-8-2-000-WEB-1.pdf