You can conjecture that Handel didn't write "The Messiah".
You can conjecture that Newton didn't formulate the law of universal
gravitation.
You can conjecture that Biot&Savart didn't originate the law of
Biot&Savart.
But in the absence of evidence, these aren't very interesting
conjectures.
Saying that somebody else "could" have done it isn't evidence.
Saying that somebody else did something similar isn't evidence.
If contemporaries had objected that the B-S law was mis-attributed,
that would be interesting. But precisely no evidence of this sort
has been adduced. If M. Ampère was content to attribute it to B&S,
why should we question it now?
There were lots of competent physicists active in the 1820s. You
could pick any one of them at random and conjecture that he alone
originated all the interesting results. But why would you want to?
The B-S law is vastly more generally useful than Ampère's law. The
latter is cute, but not particularly useful for calculations, except
perhaps for toy problems with high symmetry. Ampère's law is not a
particularly obvious corollary of the B-S law. And the B-S law is
certainly not a corollary of Ampère's law.
There are a !!few!! references that integrate both sides of the B-S
law and call the result the Ampère-Laplace law, but this usage appears
to be confined to Europe and is exceedingly rare even there. This is
such an obvious corollary that I don't see why it needs a name at all.