If you take a look at this webpage about blocked ports, you'll notice that Spectrum says nothing about blocking port 23 but they do:
https://www.spectrum.net/support/internet/blocked-ports
| Sysop: | deepend |
|---|---|
| Location: | Calgary, Alberta |
| Users: | 326 |
| Nodes: | 10 (0 / 10) |
| Uptime: | 27:09:05 |
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| Calls today: | 4 |
| Files: | 6,608 |
| D/L today: |
135 files (33,187K bytes) |
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