Unexpected dig +trace behavior

I am trying to find the nearest parent DS record for a domain, and I'm running into an issue that seems to be related to the synth address. The following works to find the DS records of the parents of www.isc.org.

```
➜ ~ dig @8.8.8.8 +trace www.isc.org | grep -w 'IN[[:space:]]*DS'

org. 86400 IN DS 26974 8 2 4FEDE294C53F438A158C41D39489CD78A86BEB0D8A0AEAFF14745C0D 16E1DE32
isc.org. 86400 IN DS 7250 13 2 A30B3F78B6DDE9A4A9A2AD0C805518B4F49EC62E7D3F4531D33DE697 CDA01CB2
```

But this does not work with my HSD recursive resolver running on port 53.
```
➜ ~ dig @127.0.0.1 +trace www.isc.org | grep -w 'IN[[:space:]]*DS'

dig: couldn't get address for '_fs00008._synth': no more
```

Came across [this issue](https://github.com/handshake-org/hsd/issues/400), and after configuring my hsd resolver in /etc/resolv.conf, the error disappears, but I do not got the expected response.

```
➜ ~ dig +trace www.isc.org | grep -w 'IN[[:space:]]*DS'
➜ ~
```

```
➜ ~ dig +trace www.isc.org

; <<>> DiG 9.11.26-RedHat-9.11.26-6.el8 <<>> +trace www.isc.org
;; global options: +cmd
. 515920 IN NS _fs00008._synth.
. 8320 IN RRSIG NS 13 0 518400 20230106011014 20220105011014 60944 . a651SserHwmby4rcVMsGMHAJLYAyBxLzrN1v7E4C+JE66Dz7zyP8ViK/ 8x0hebV5z4CMqOfX7zEFtpxPNy6G9g==
;; Received 256 bytes from 66.42.108.201#53(66.42.108.201) in 1 ms

www.isc.org. 200 IN CNAME dualstack.osff2.map.fastly.net.
www.isc.org. 200 IN RRSIG CNAME 13 3 300 20220123151519 20211224144419 27566 isc.org. QSz8TD9BvYxxQAS3OuatwDISaabQoqlVqH872T2adlty75gk7QQsiDLA vRseeGxzseaxkP7CYzCH365SaixmtA==
dualstack.osff2.map.fastly.net. 15 IN A 151.101.198.217
;; Received 302 bytes from 127.0.0.1#53(_fs00008._synth) in 1 ms
```

It also does not work for on chain TLDs. I have a single DS record on the blockchain for `ns9`.

```
➜ ~ dig ns9 DS
...
;; ANSWER SECTION:
ns9. 18612 IN DS 1 15 0 1FBC442BD3F7F5D5D6DCC3FD90EB67CF732A45525171752B3957BA27 835BC6CD
...
```

However, the DS record is absent from the trace.
```
➜ ~ dig +trace ns9 | grep -w 'IN[[:space:]]*DS'
➜ ~
```

```
➜ ~ dig +trace ns9

; <<>> DiG 9.11.26-RedHat-9.11.26-6.el8 <<>> +trace ns9
;; global options: +cmd
. 514976 IN NS _fs00008._synth.
. 7376 IN RRSIG NS 13 0 518400 20230106011014 20220105011014 60944 . a651SserHwmby4rcVMsGMHAJLYAyBxLzrN1v7E4C+JE66Dz7zyP8ViK/ 8x0hebV5z4CMqOfX7zEFtpxPNy6G9g==
;; Received 256 bytes from 127.0.0.1#53(127.0.0.1) in 1 ms

ns9. 18404 IN NSEC ns9\000. RRSIG NSEC
ns9. 7604 IN RRSIG NSEC 13 1 21600 20230106011402 20220105011402 60944 . rlFhaSa+vbtDsM9FXGv9Zd7muco3aoexhO25LD9xzctuDaEwSLnsFo9s toDSwQKQqY1LzK3RWK8yaa+3Godnww==
. 83204 IN SOA . . 2022010601 1800 900 604800 21600
. 7604 IN RRSIG SOA 13 0 86400 20230106011402 20220105011402 60944 . Hhin3It1ZIVK1d8A/L6Cg2mHErtMMB0xV4DT470gU6Rdx/jmQ39po6cy vYoJd2Jh5kMLID+6XrG3noXPnMbCOA==
;; Received 386 bytes from 127.0.0.1#53(_fs00008._synth) in 1 ms
```

Is this an issue with the recursive resolver returning an incomplete response, or is it tied up with the synth address root server?