Comment 1 for bug 1909800

SBCL has had the SEQUENCE package for >= 15 years, and I'm disinclined to add "equivalent" features.
Personally I'd suggest that your code do #+sbcl (pushnew :extensible-sequence *features*) if you think it will help either your system or dependents on your system.
Granted, the spec says that ":ieee-floating-point" is present if IEE754 is supported, despite it being standard since 1985. But I think the distinction is that there isn't a simple way to detect use of non-IEE754 floats, and SBCL could theoretically support whatever that other thing is. Whereas, an extra feature for sequences would mean literally no more and no less than the :sbcl feature already conveys.

If others developers disagree with me, I won't object to adding it; but I don't see it as a good solution to anything, just an annoyance, as I'm already striving to _remove_ extraneous features.