tails-get-network-time sets different User-Agent than NetworkManager
tcpdump shows that tails-get-network-time
sends this User-Agent:
User-Agent: PycURL/7.43.0.6 libcurl/7.74.0 GnuTLS/3.7.1 zlib/1.2.11 brotli/1.0.9 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.3.0) libssh2/1.9.0 nghttp2/1.43.0 librtmp/2.3
At least on my system (sid), NetworkManager doesn't send any User-Agent.