Having had the opportunity to flick through BPlan, I suspect that there's a data error with the Timing Load that is causing RTT to misreport it. There's no loco-hauled timing load with a trailing load of 325t in the data I can see.
I am fairly sure they at least were timed as Class 325 EMU in TPS. Not that it's especially important.
As per the post above, the "loco-hauled" aspect is related to how the reporting was normally done for the 325s in TOPS on Royal Mail duties. They were effectively consisted as "freight trains without a loco" (and occasionally with a loco) in the same way as the loco-hauled mail trains. MPV circuits are also often shown as loco-hauled. This is a bit of a "fudge" with how the schedule is set up in TRUST / TOPS which may be different from how it looks in the planning systems.
Multiple unit schedules can cause issues with TOPS because they expect the consist entry to come either from systems that only the TOCs use, or from POIS inputs (passenger equivalent of TOPS) which can be more temperamental than using regular TOPS. I remember there were some oddities where if an MPV was running on a multiple unit schedule, in some cases it wouldn't accept a consist due to the system insisting that a POIS input was invalid for a class 6 train, or it didn't accept YXAs being freight stock on what it thought should be a passenger train headcode or train category - I can't quite remember but there were one or two annoying incompatibilities along those lines...
1M36 schedule in TRUST, showing much the same info as RTT (loco-hauled, 325 timing load. PV = Parcels Vans):
Train 071M36M runs MSX from 06/10/26 to 11/12/26 - Auto-Call
Train category PV Loco-Hauled 309 miles Applicable Timetable Service
Train service code 55460080 Catering N/A
Uid C01664 Sector 54 Sub-sector 02 Set up by TSDB on 09/10/26 Type WTT
Location Booked C Pw Miles Tlod Ctg Pfm Eng Pth Consist
07915 SHIELDMR 08:42 325 1 ORIGINATING PT
07972 ABINGTON 09:05 09:15 0 29 5 9 CALLING POINT
35531 WARRTN BQ 11:28 11:30 0 204 2 5H CALLING POINT
42128 CWECOALYD 11:57 12:08 0 228 3H CALLING POINT
42140 CREWE 12:13 12:26 0 228 2 6H CALLING POINT
70081 DAVTRYREC 13:45 309 TERMINATING PT
Varamis 1M04 WTT path set up as a multiple unit schedule with a 321 timing load (XU = express passenger train, unadvertised):
Train 071M04M runs FSX from 18/05/26 to 10/12/26 - Manual-Call
Train category XU Multiple-Unit 292 miles Applicable Timetable Service
Train service code 59980001 Catering N/A
Uid C08651 Sector 95 Sub-sector 05 Set up by TSDB on 09/10/26 Type WTT
Location Booked C Pw Miles Tlod Ctg Pfm Eng Pth Pcnt TI
07360 MOSSND DY 17:45 321 3 3H
09161 CARLISLE 18:57 18:59 0 92 8 19H
69215 BHAM INTL 21:57 292