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Some further info on Telnet. Port 23 is not the only port used. Port 107 is used by Remote Telnet.
Also there is a way to shut down all Telnet activity using the Eset firewall. You would have to create a firewall rule to block all inbound and outbound activity specifying the protocol as "Custom" and the protocol number as 240 - 255. In other words, 15 firewall rules would be needed since the Eset firewall only also one protocol number to be specified per firewall rule.
Ref.: http://www.networksorcery.com/enp/protocol/telnet.htm

To be 100% accurate in regards to telnet is the following. The telnet client is not installed on Win 10 by default: https://www.rootusers.com/how-to-enable-the-telnet-client-in-windows-10/ . As noted in the article if the telnet client is installed, any port can be used by it; not just port 23.
When router's reference telnet, they are just referring to its default use of port 23. Disabling the telnet option on the router is just blocking all inbound/outbound WAN side port 23 TCP/UDP traffic to/from the router.
When the router is set to bridge mode, you are  instructing the router to pass all inbound and outbound traffic through the WAN side of the router. All firewall, IDS, and protocol filtering methods on the router are disabled. Additionally, both NAT and stateful transmission detection are also disabled on the router. As such, you are now relying 100% on Eset's firewall for port 23 protection. Whereas Eset's firewall will block an unsolicited inbound port 23 traffic by default, such is not the case for any outbound port 23 traffic. By default, Eset allows all outbound traffic.