Provide clarification between SHM and GPSD client drivers, reason for GPSD exclusion in Debian-provided packages?

I'm please curious for more details as to the preferences between the SHM and GPSD client drivers?

As I understand the Debian maintainer (@rlaager) is part of the ntpsec project here as well, I'm specifically wondering if there is any reason why the GPSD driver is not included in the Debian provided version - or if it could please be included? (If it would introduce a runtime dependency on gpsd at all, could an alternate version then also be provided?)

Personally, I kind of like seeing the 2 rows in the GPS status, currently as such:

$ ntpq -pn
     remote           refid      st t when poll reach   delay   offset   jitter
===============================================================================
oPPS(0)          .kPPS.           0 l   34   64  377   0.0000   0.0022   0.0003
*SHM(0)          .SHM.            4 l   39   64  377   0.0000  -2.8539   6.2192

However, from https://docs.ntpsec.org/latest/driver_shm.html :

Note: The GPSD client driver uses the GPSD client protocol to connect and talk to GPSD, but using the SHM driver is the ancient way to have GPSD talk to ntpd. There are some tricky points when using the SHM interface to interface with GPSD, because GPSD will use two SHM clocks, one for the serial data stream and one for the PPS information when available. Receivers with a loose/sloppy timing between PPS and serial data can easily cause trouble here because ntpd has no way to join the two data streams and correlate the serial data with the PPS events.

and from https://www.ntpsec.org/drivers.html :

Types 28 and 46 are no-brainers to keep. We will eventually want to deprecate the SHM driver in favor of the JSON one. That needs to be described as a future direction in the documentation.

Both above points make sense to me. (The 2nd does not extend into a reason, but I'd assume it is a repeat of the 1st?)

Yet, the current Debian provided ntpsec ntpd binaries are compiled without GPSD:

$ ntpd --help
...
This version was compiled with the following clock drivers:
       LOCAL  SPECTRACOM     GENERIC     ARBITER        NMEA
         PPS       HPGPS         SHM     TRIMBLE         JJY
       ZYFER

$ apt list ntpsec
Listing... Done
ntpsec/buster-backports,now 1.1.9+dfsg1-2~bpo10+1 armhf [installed]

This led me down the rabbit hole of compiling my own ntpsec, leading to #667 (closed) and related complications. There, @jamesb_fe80 also replied opposite of the above:

Also the SHM driver is generally considered better than the gpsd over local TCP driver.

(I had also asked about this on IRC at #ntpsec, which led to the posting here.)

Please advise? Thanks!