I'd not bother thinking about it for other than navigational purposes.
Fully agree G - unless you are one of those people that write sales guff.
While IAS and the dynamic pressure it represents is without doubt the prime stress producing number, in the very small print there may be trim change effects associated with mach number or possibly even flutter considerations which require an altitude limit. In the smallest print of all an altitude limit may represent the envelope of testing or "don't exceed than son as we simply have not tried it"