Installing the Figure numbering extension slows down all page rendering a lot

To reproduce:

• Install the Figure numbering extension
• Create an empty page
• Open chrome dev tool on the network tab
• Enable caching and refresh a few times the page, notice the total execution time (for me it's about 2 seconds)
• In the list of request, find the http://localhost:8080/xwiki/bin/ssx/NumberedFigures/Code/NumberedFigures?isNumberedFiguresEnabled=false&locale=en&docVersion=1.1 one and block right (right click and select "block request url")
• Refresh again and notice that when it's blocker the page takes a lot less time to render (1s in total for me vs 2s when it's not blocked)

Screenshot 1: without blocking the ssx (1.91s):

Screenshot 1: with blocking the ssx (963ms):