Well, that may be true, but when the bolt-action came to be in 1829 (Dreyse), virtually all other military arms were muzzle-loaders which, I am sure you recognize, makes it by necessity a single-shot save for revolver-based actions where the entire action revolved, or multiple-barrels.
Of course, I'm sure you recognize that the repeaters in the Civil War held more than 4 rounds as a general rule, and the same can be said for most early repeaters. When power increased, magazine capacity dropped. But saying that when bolt-action rifles came out, most rifles were single shots is a bit short of the mark and quite an understatement. When bolt-action rifles came out, there were very few breach-loaders in existence (though breach loading had been about a while already). As the vast majority of arms in 1829 were still muzzle-loading, it is kind of stating the obvious that they were single shots.