That means, a ECC_nistP384 application instance certificate can
use ECC_nistP384 and ECC_nistP256 security profiles, but from
the profile reporting tool this information either disallows that
or is at least misleading:

ECC-nistP256_Limits:
-> DerivedSignatureKeyLength = 256
-> EncryptionKeyLength=128
-> InitializationVectorLength=128
-> SignatureLength=256
-> MinAsymmetricKeyLength = 256 (ECC)
-> MaxAsymmetricKeyLength = 384 (ECC for CA Only)
-> SecureChannelNonceLength = 64

This should be MaxAsymmetricKeyLength = 384 (ECC)
and the AsymmetricSignatureAlgorithm_ECDSA-SHA2-256
should make it cleat that the signature length is
64 bytes for nistP256 keys and 96 bytes for nistP384 keys
but hash function SHA2-256 is used in any case.
Only a mistP256 key cannot be used to create signatures
for the ECC_nistP384 profile.

Likewise ECC_brainpoolP256r1 and ECC_brainpoolP384r1 were meant
to be interoperable.