Why doesn't an Excel spreadsheet stay locked and protected when opened in Mac Numbers?

[SuziChoclat]

Hello Tech Team

Not sure what I am doing wrong so asking for some help. On a Microsoft laptop I maintain an excel spreadsheet with information, I save it with locked cells and password protection, giving only sort and filter functions. A colleague then adds it to our website behind a button for public viewing. When I view our website on my Mac computer and click on the button, the spreadsheet downloads and opens in Numbers without any protection at all. I can edit, delete, rename and do anything as if the spreadsheet was created in Numbers. Why would this be happening? I would like it fully protected in Mac as it is when downloaded in Microsoft. 

Thank you 
Suzi

[#2]

You're using an Excel feature that appears to have no equivalent in the Mac app. Sheet level protection is programmed into the xml for the sheet in an xlsx. An app that cannot read this will not uphold this security.

[#3]

Thank you Patrick, do you know if is there is any way around this? Can I protect differently or add to website in a different way?
Thank you