in the example given, if a block is placed/moved ontop the redstone torch, the adjacent redstone dust will power, the block will be pushed away by the piston and the powered rail will also power. however the observer will not be able to detect this. this behaviour does not change if the rail is replaced by a noteblock or fencegate.

in 1.19.4 the observer is able to detect the powered rail powering and will power the second piston.

this currently breaks alot of 4 game tick block conveyors