Yes and no. The rate of flashing is determined by the total resistance the flasher sees. You can mimic the load or buy a flasher that the rate of flashing is not determined by the load.

There is also a chance those lights have already incorporated an internal load in production. So the older flashers see them as normal light bulbs.

You will know instantly when you hook them up. In your lifetime you have seen the rapid flashing rate when one turn signal bulb is burnt out or has circuit problems. A couple of light bulbs painted black can duplicate the load by wiring each across the two circuits. Can be hidden almost anywhere. I did not price or ever buy what I describe as a no load dependant flasher. They do exist and may be very common today.