well. 1 guy might not do anything.
but it does pump processes pretty fast. data that has to be uploaded and downloaded to everyone in the server.
Let's say there's at least 500 bytes required to be sent to each player if someone changes their avatar.
If the shirt changes 10 times per sekond, that is 5000 bytes.
If there are 20 people in the server, that is 100000 bytes.
If all 20 people have it, that is 2000000 bytes.
That is almost
2 megabytes per sekond of data the server must send out.
Lukly default restriktions mean even servers without the anti-funky add-on won't be seeing quite 10 per sekond. By default I think it's limited to like, two per sekond, but idk.
And of course, getting all 20 people to use it is unlikely also.