I have no idea what you are talking about regarding Safari ignoring "filter: blur()" - it's supported it since 2012, just a few months after Chrome added it. In fact - I think at the time Chrome was still using Webkit.

"backdrop-filter" is a completely different thing. Rather than filtering the element itself, it filters all elements behind it. This is especially useful with blur. While you are correct that Safari is the only browser currently supporting it, it is part of the standard, although it's not yet finalized. Chrome also supports it if you enabled "Experimental Web Features"