I’m guessing his backstory is that he was an esper and was broken and rebuilt into a super guide but the original intent was probably to make a super esper so he might be really compatible with the guides of fated bonds rather than the espers but it’s far easier to brute force an esper who is unstable than a guide who is stable.
If we compare the esper and guide verse to periodic elements, espers are the ever unstable hydrogen or magnesium or sodium while guides are like fluorine or chlorine. They are almost stable. While trying to make a super super stable (helium) esper, the doctor found it easier to start from a guide base since it would be the difference of 7 to 8 instead of 1 to 8 and then he can switch the guide to an esper. At least that’s my theory of how it works. I could be completely wrong and overthinking all of this.
Not created for espers? Then what? For guides? ╮(￣▽￣)"╭