(use-)alt-transfer-source deprecated

[Gasoo]

Hello

I recently updated to 9.18.x and noticed the deprecation warning in the 
logs for the option use-alt-transfer-source.
After reading the manual and checking my configuration, I am confused on 
how this is going to work in future releases.

My configuration includes the following statements:

options {
   listen-on { 1.1.1.1; 2.2.2.2; 3.3.3.3; };
   transfer-source  3.3.3.3;
   query-source  3.3.3.3;
   notify-source  3.3.3.3;
   use-alt-transfer-source no;
   ...
}


1.1.1.1 and 2.2.2.2 are only used for incoming DNS queries from clients 
and can not be used for zone transfers.
If I remove the option use-alt-transfer-source, in some cases (e.g. 
SERVFAIL from primary), additional zone transfers are tried via 
0.0.0.0#0, which the OS then sends via the best matching interface / IP 
address.

For this reason the option use-alt-transfer-source is in my configuration.


 From the manual.

use-alt-transfer-source:
This indicates whether the alternate transfer sources should be used. If 
views are specified, this defaults to no; otherwise, it defaults to yes.
alt-transfer-source:
This indicates an alternate transfer source if the one listed in 
transfer-source fails and use-alt-transfer-source is set.


How will this be handled in future releases, if transfer-source is 
specified, no views are defined and an error occurs?
Is there any other solution to disable transfers from 0.0.0.0#0 in my case?


Kind Regards
Stephan