Yeah, just as you imply I pretty much stole the system from soulslikes :P (stamina bar included, heh)
A lot of older scrolling beat 'em ups have basically no mechanics to speak of, you do the same handful of actions all the time (you'd think with 6 total face/shoulder buttons on a SNES controller there'd be more than basic attacks, jumps and the "hurt yourself for dubious benefit" special move button so many of them stuck with) so I felt like I had to expand on it somehow... also I suck at character animation so I wanted to keep the number of attack animations low; the single-frame shield/dash poses were perfect for this.
I feel like soulslikes are basically a combination of scrolling beat-em-ups and metroidvanias so it'd be interesting seeing if more indies realize the potential of backporting mechanics going forward - we've got the River City Ransom reboot and one of the UFO 50 games both adding a couple modest RPG elements to a scrolling beat 'em up, far from a big trend but it's something.