I think we need to keep this bridge until we remove the deprecated methods that are still using ConfigProperties

I think we need to keep this bridge until we remove the deprecated methods that are still using ConfigProperties

No those are not using this bridge - use explicit fallback instead.

In fact, only contrib extensions use this bridge at this point.

what if someone has an extension with

• IgnoredTypesConfigurer
• InstrumentationModule

using one of those deprecated ConfigProperties methods?

what if someone has an extension with

• IgnoredTypesConfigurer
• InstrumentationModule

using one of those deprecated ConfigProperties methods?

That's a good point. We have to decide if we want to support ConfigProperties in those extensions together with declarative config, which is still experimental.
I would say we sholudn't try to do that, it only creates some things that still don't work - like the new "distribution" node support added in #15822.