Using Apple hotspot to do the port scan, found 21 port is always open, would like to know is there anything special setting in Apple Hotspot service?

To whom it may concern,

I used a famous website "www.redhat.com" to test the nmap scan by using a laptop which is connected to apple's hotstpot, and find the port 21 is open, but using other network, the port 21 is not opened, may I know if there is any special setting in Apple hotspot makes this weird behavior?

----My scan result here--

Nmap scan report for www.redhat.com (23.7.212.225)

Host is up (0.020s latency).

rDNS record for 23.7.212.225: a23-7-212-225.deploy.static.akamaitechnologies.com

Not shown: 997 filtered tcp ports (no-response)

PORT    STATE SERVICE  VERSION

21/tcp  open  ftp?

80/tcp  open  http     AkamaiGHost (Akamai's HTTP

Acceleration/Mirror service)

|_http-title: Access Denied

| http-methods:

|_  Supported Methods: GET HEAD POST

443/tcp open  ssl/http AkamaiGHost (Akamai's HTTP Acceleration/Mirror

service)

| ssl-cert: Subject: commonName=www.redhat.com/organizationName=Red

Hat, Inc./stateOrProvinceName=North Carolina/countryName=US

| Subject Alternative Name: DNS:www.redhat.com

| Issuer: commonName=DigiCert SHA2 Extended Validation Server

CA/organizationName=DigiCert Inc/countryName=US

| Public Key type: rsa

| Public Key bits: 2048

| Signature Algorithm: sha256WithRSAEncryption

| Not valid before: 2022-09-13T00:00:00

| Not valid after:  2023-09-15T23:59:59

| MD5:   ac81d641d94ade33806539de26d6eedd

|_SHA-1: c930a2d3ae5664611edbeef20bfe307eb3e455ba

|_ssl-date: TLS randomness does not represent time

|_http-title: Access Denied

| http-methods:

|_  Supported Methods: GET HEAD POST

Warning: OSScan results may be unreliable because we could not find at least 1

open and 1 closed port

OS fingerprint not ideal because: Missing a closed TCP port so results

incomplete

No OS matches for host

Uptime guess: 0.001 days (since Wed Jan  4 23:27:01 2023)

Network Distance: 10 hops

TCP Sequence Prediction: Difficulty=261 (Good luck!)

IP ID Sequence Generation: All zeros