When the newly introduced `"maxfeerate"` option is not passed, the default fee rate is interpreted as an absolute amount. However, when it is passed, it is interpreted as a fee rate. Thus, the rpc will return different results when the value is explicitly set to the default.

See

https://github.com/bitcoin/bitcoin/blob/536590f358dc3d3e5821eba7f1009452ea93b205/src/rpc/rawtransaction.cpp#L797-L807

I think we should change it back to an absolute value in BTC (not a feerate)

This was changed to a feerate by @kallewoof, so ping him to see if there was a specific reason to switch.
return EncodeBase64((unsigned char*)ssTx.data(), ssTx.size());
}
UniValue analyzepsbt(const JSONRPCRequest& request)
{
            RPCHelpMan{"analyzepsbt",
            "\nAnalyzes and provides information about the current status of a PSBT and its inputs\n",
            {
                {"psbt", RPCArg::Type::STR, RPCArg::Optional::NO, "A base64 string of a PSBT"}
            },
            RPCResult {
                "{\n"
                "  \"inputs\" : [                      (array of json objects)\n"
                "    {\n"
                "      \"has_utxo\" : true|false     (boolean) Whether a UTXO is provided\n"
                "      \"is_final\" : true|false     (boolean) Whether the input is finalized\n"
                "      \"missing\" : {               (json object, optional) Things that are missing that are required to complete this input\n"
                "        \"pubkeys\" : [             (array, optional)\n"
                "          \"keyid\"                 (string) Public key ID, hash160 of the public key, of a public key whose BIP 32 derivation path is missing\n"
                "        ]\n"
                "        \"signatures\" : [          (array, optional)\n"
                "          \"keyid\"                 (string) Public key ID, hash160 of the public key, of a public key whose signature is missing\n"
                "        ]\n"
                "        \"redeemscript\" : \"hash\"   (string, optional) Hash160 of the redeemScript that is missing\n"
                "        \"witnessscript\" : \"hash\"  (string, optional) SHA256 of the witnessScript that is missing\n"
                "      }\n"
                "      \"next\" : \"role\"             (string, optional) Role of the next person that this input needs to go to\n"
                "    }\n"
                "    ,...\n"
                "  ]\n"
                "  \"estimated_vsize\" : vsize       (numeric, optional) Estimated vsize of the final signed transaction\n"