Timing Loads dont indicate any actual diagrammed stock.
we understand that. Hence why Class 802's and HST's were running to HST timing loads on the routes out of Paddington.
Due to a shortage of rolling stock, Anglia timing loads for an electric loco hauling 350 tons can be run by a pair of class 321's. But if the 90's are avail;able, that is what gets used!
On the East Coast, HST and Electric loco timing loads generally find an HST on a timing load that says HST, and a 91 or a 90 hauling mk4 stock where it is specified Electric loco hauling xxx tons. But a HST can substitute and vice versa if there is a shortage of rolling stock. But you won't find an HST on an edinburgh turn with an electric loco as the booked timing load if a Class 91 is available.
So most of the time the timing loads are an indication of what stock the TOC intends to use. They are the ones that submit their timetable request to Network rail.
You will find anything that has been planned in to be run by a DMU, comes up as 'sprinter' within the timing loads. And probably more guaranteed that the booked DMU will turn up as opposed to an HST!