Well it’s not the same in a similar fashion of “1 + 1 = 2” is not literally the same as “3 - 1 = 2”. Maybe they accomplish similar goals but downshifting to brake can be done for as many gears as the transmission contains in a stepwise fashion. But without a transmission in a single speed vehicle with regenerative braking it’s more of a “spectrum” of braking and not directly controllable by the driver.

And for the record I believe “engine braking” is a slightly different mechanism than “downshift braking” but could be wrong here - my manual passenger vehicles don’t have explicit “engine brake” controls but a semi truck might.