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.
keypaths.push_back(keypath);
            }
            in.pushKV("bip32_derivs", keypaths);
        }
        
        if (!input.final_script_sig.empty()) {
            UniValue scriptsig(UniValue::VOBJ);
            scriptsig.pushKV("asm", ScriptToAsmStr(input.final_script_sig, true));
            scriptsig.pushKV("hex", HexStr(input.final_script_sig));
            in.pushKV("final_scriptSig", scriptsig);
        }
        if (!input.final_script_witness.IsNull()) {
            UniValue txinwitness(UniValue::VARR);
            for (const auto& item : input.final_script_witness.stack) {
                txinwitness.push_back(HexStr(item.begin(), item.end()));
            }
            in.pushKV("final_scriptwitness", txinwitness);
        }
        
        if (input.unknown.size() > 0) {
            UniValue unknowns(UniValue::VOBJ);
            for (auto entry : input.unknown) {
                unknowns.pushKV(HexStr(entry.first), HexStr(entry.second));
            }
            in.pushKV("unknown", unknowns);
        }
        inputs.push_back(in);
    }
    result.pushKV("inputs", inputs);