I see a relay external to the IC in two of the schematics, however I see no IC in this one of your links
under the Turn Signal Hazard Flasher paragraph. The Hybrid Flasher section shows no relay.
Also described is the bimettalic flasher.
I’ll take your word that the can either contains both a control IC and a flasher relay or a relay controlled by an external IC. What you’re saying seems consistant with what most of the schematics.
Comsider me a more enlightened man.
The IC is there, it’s even labeled as “IC-1”.
The hybrid flasher section does show a relay. It is labeled as K1 (“K” is the normal reference for a relay). The contacts are shown at the top of the schematic. The relay coil is shown (with non-standard [for the US] symbol) at the bottom of the schematic. The relay is also mentioned in the text description below the schematic.
I am surprised that it is not solid state, eliminating the relay contacts which pit and arc, likely creating a little radio frequency interference upon each opening, and eventually wear out.
Would be easier on the filament to ramp up the voltage and ramp it down rather than instant full voltage.
Even better would be to keep the voltage at a certain level during the OFF phase so the filament does not go completely out (if it does) and therefore reduce shock on the filament.