Pretty sure I am not mis-remembering ... because I went out to the garage to check. The thunmb-shifters might have been an earlier version ... i forget the number, I know I ordered a set and sent them back when they had a thumb-shifter but I think those were 7-speed.

But ... I went on a tour which used 2015 Dawes Sheila PRO bikes equipped with "Shifters: Shimano ST-2300/2303 shifters integrated into brake levers, 24-speed Triple" .... I brought one home and swapped the shifters to another bike. The shifters say Claris, the time period and the purchase agreements say 2300 .... but whatever. if his have thumb buttons and are 2300, then Shimano made both types using the 2300 name.