I can confirm that gravity shunting was extensively resorted to in the days when the line was steam operated and even, occasionally, after the D63XX diesels took over. The trucks could be either side of the engine but I don’t recall coaching stock being dealt with this way. The gradient into the Station was such that trucks could pick up a fair lick and would have the shunter running alongside to apply the brake.
The most obvious use was for getting empty coal trucks and the odd truck-full of ash and cinders out of the Engine Shed siding, to be replaced with a full truck of coal. Many and various routines were used seemingly down to the combined ingenuity of the footplate crew, guard, signalman and shunter-porter, and what had to be done and how much space was available where. There would be much tooting of whistles and rushing about, at which the 45XXs were particularly adept. I did sometimes wonder if the Rule Book was being followed to the letter! I will leave you to work out how this could be accomplished but bear in mind that the station was extremely cramped, especially in the summer months when extra coaches were usually lying about as well as covered wagons of advance luggage.
Regrettably my parents moved away from St Ives in 1964 but by then the signalling had been removed and with it any excitement.