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 result;
}
static const CRPCCommand commands[] =
{ 
  
    { "rawtransactions",    "getrawtransaction",            &getrawtransaction,         {"txid","verbose","blockhash"} },
    { "rawtransactions",    "createrawtransaction",         &createrawtransaction,      {"inputs","outputs","locktime","replaceable"} },
    { "rawtransactions",    "decoderawtransaction",         &decoderawtransaction,      {"hexstring","iswitness"} },
    { "rawtransactions",    "decodescript",                 &decodescript,              {"hexstring"} },
    { "rawtransactions",    "sendrawtransaction",           &sendrawtransaction,        {"hexstring","allowhighfees|maxfeerate"} },
    { "rawtransactions",    "combinerawtransaction",        &combinerawtransaction,     {"txs"} },
    { "rawtransactions",    "signrawtransactionwithkey",    &signrawtransactionwithkey, {"hexstring","privkeys","prevtxs","sighashtype"} },
    { "rawtransactions",    "testmempoolaccept",            &testmempoolaccept,         {"rawtxs","allowhighfees|maxfeerate"} },
    { "rawtransactions",    "decodepsbt",                   &decodepsbt,                {"psbt"} },
    { "rawtransactions",    "combinepsbt",                  &combinepsbt,               {"txs"} },
    { "rawtransactions",    "finalizepsbt",                 &finalizepsbt,              {"psbt", "extract"} },
    { "rawtransactions",    "createpsbt",                   &createpsbt,                {"inputs","outputs","locktime","replaceable"} },
    { "rawtransactions",    "converttopsbt",                &converttopsbt,             {"hexstring","permitsigdata","iswitness"} },
    { "rawtransactions",    "utxoupdatepsbt",               &utxoupdatepsbt,            {"psbt", "descriptors"} },
    { "rawtransactions",    "joinpsbts",                    &joinpsbts,                 {"txs"} },
    { "rawtransactions",    "analyzepsbt",                  &analyzepsbt,               {"psbt"} },
    { "blockchain",         "gettxoutproof",                &gettxoutproof,             {"txids", "blockhash"} },
    { "blockchain",         "verifytxoutproof",             &verifytxoutproof,          {"proof"} },
};
void RegisterRawTransactionRPCCommands(CRPCTable &t)
{
    for (unsigned int vcidx = 0; vcidx < ARRAYLEN(commands); vcidx++)
        t.appendCommand(commands[vcidx].name, &commands[vcidx]);
}