You better ask Gunther (GoodGuy)
*Cough* ... Gunnar ...
I believe these 10 aarm rounds used in the Estab for 10.5cm leFH 18/40 are representing 10cm Pzgr Rot L'Spur shells. You better ask *COUGH* (GoodGuy) whether these were historically used in field artillery loadouts in 1944 or not. To my knowledge, at least in Summer 1941 these were not available to regular German field artillery crews (who therefore had to use HE rounds against Soviet tanks until later in 1941 HEAT rounds became available, however in very limited quantities)
Hitler ordered the production of hollow-charge rounds in December 1941, which were then to be used in tanks and PaKs. The first tank units received those rounds in January 1942, which came in 2 flavors, the 75-mm variant for the KwK 37 (the short-barreled gun on the Pz.IV) and the PaK 40 and - later on - the 88-mm variant for the KwK 36 on the Tiger. The round was referred to as Pz.Gr. 38 HL, but quite a few contemporary sources seem to refer to it as Pz.Gr. 39 HL. A revision (38 HL/B) was available in September 1942, another improved version (38 HL/C) either in '43 or '44.
German crews usually refrained from using the HL-grenades with guns that provided somewhat higher velocities (ie. on the Tiger or the PaK), as the long barrels and the high(er) velocities resulted in a pretty toned down penetration performance of those HL-grenades - so the regular AP grenades were preferred.
Afaik, Leichte FH 18 units received 10.5-cm variants of the Pz.Gr.HL. The gun's mediocre muzzle velocity (470 m/sec) might have produced fair/good results when used in an AT-role. The units also received regular Pz.Gr. (AP) rounds, possibly after Hitler had ordered the production of the HL-rounds, means sometime during 1942. Afaik, a regular gun outfit would contain a number of AP rounds and one or another HL round.