Bridge Authority never assigns a Stable flag to bridges

I found out about this behaviour in tpo/network-health/metrics/relay-search#33493

Apparently the Bridge Authority hasn't been assigning a Stable flag to bridges for quite some time. I'm not sure whether this is on purpose or a bug.

torrc file (with IPs and contact info scrubbed):

SocksPort 0
Log notice file /var/log/tor-notice.log
#Log info file /var/log/tor-info.log
RunAsDaemon 1
DataDirectory /var/tor
Address [scrubbed]
ORPort [scrubbed]
ORPort [scrubbed]
OutboundBindAddress [scrubbed]
DirPort [scrubbed]
Nickname Serge
RelayBandwidthRate 5500 KBytes
RelayBandwidthBurst 6500 KBytes
User _tor
ExitPolicy reject *:*
ExitPolicy reject6 *:*
PublishServerDescriptor 1
HeartbeatPeriod 1 hours
AvoidDiskWrites 1
NumCPUs 4
ContactInfo [scrubbed]

AuthoritativeDirectory 1
BridgeAuthoritativeDir 1

AuthDirHasIPv6Connectivity 1

EntryStatistics 1
DirReqStatistics 1