Server listens on more than 2 ports when server.properties is configured to use non-default ports.

I noticed an issue with the BDS when I was trying to run multiple instances on the same machine. Essentially, if you use the default ports, everything is better, however, if you change the server.properties to listen to any ports other than the defaults, it will listen to 4 ports, the 2 default ones and the 2 configured ones:

For example - Server configured to listen to non-default ports 19134 and 19135

server.properties snippet

server-port=19134
server-portv6=19135

log shows

[2020-04-23 14:30:53 INFO] Starting Server
[2020-04-23 14:30:53 INFO] Version 1.14.60.5
[2020-04-23 14:30:53 INFO] Session ID 22bfa959-ee90-4c41-9c95-9a3516040217
[2020-04-23 14:30:53 INFO] Level Name: DimitrovLand
[2020-04-23 14:30:53 INFO] Game mode: 0 Survival
[2020-04-23 14:30:53 INFO] Difficulty: 1 EASY
[2020-04-23 14:30:53 INFO] Content logging enabled. Writing log to: ContentLog__Thursday__2020_April_23__14_30_53
[2020-04-23 14:30:53 INFO] opening worlds/DimitrovLand/db
[2020-04-23 14:30:55 INFO] IPv4 supported, port: 19134
[2020-04-23 14:30:55 INFO] IPv6 supported, port: 19135
[2020-04-23 14:30:55 INFO] IPv4 supported, port: 19132
[2020-04-23 14:30:55 INFO] IPv6 supported, port: 19133

netstat confirms that the two default ports AND the two configured ports are being opened

/minecraft-bedrock# netstat -tulpna | grep 191
udp 0 0 0.0.0.0:19132 0.0.0.0:* 6142/bedrock_server
udp 0 0 0.0.0.0:19134 0.0.0.0:* 6142/bedrock_server
udp6 0 0 :::19133 :::* 6142/bedrock_server
udp6 0 0 :::19135 :::* 6142/bedrock_server

Now, if I change it to the defaults I get the following:

[2020-04-23 14:39:43 INFO] opening worlds/DimitrovLand/db
[2020-04-23 14:39:45 INFO] IPv4 supported, port: 19131
[2020-04-23 14:39:45 INFO] IPv6 supported, port: 19132
[2020-04-23 14:39:45 INFO] IPv4 supported, port: 51917
[2020-04-23 14:39:45 INFO] IPv6 supported, port: 49167
[2020-04-23 14:39:46 INFO] Server started.

While it shows 2 extra ports in logs, it's only listening to one extra random IPv4 port

/minecraft-bedrock# netstat -tulpna | grep 191
udp 0 0 0.0.0.0:19131 0.0.0.0:* 13508/bedrock_serve
udp 0 0 0.0.0.0:51917 0.0.0.0:* 13508/bedrock_serve
udp6 0 0 :::19132 :::* 13508/bedrock_serve