mariabackup SST fails, open-files-limit limited by that of mysqld

0) galera cluster of three nodes
1) config:
[mysqld]open_files_limit is unset, i.e. using the default calculated value
[mysqld]wsrep_sst_method=mariabackup
[mariabackup]open-files-limit = 35000
2) cat /proc/<pid of mysqld>/limits | grep files
Max open files 10640 10640 files
3) find /var/lib/mysql -type f | wc -l
31303
4) start SST - it fails - /var/lib/mysql/mariabackup.backup.log on the donor says:
[00] 2020-04-12 13:33:13 open files limit requested 35000, set to 10640
...
2020-04-12 13:33:25 0 [ERROR] InnoDB: Operating system error number 24 in a file operation.
2020-04-12 13:33:25 0 [ERROR] InnoDB: Error number 24 means 'Too many open files'

[mariabackup]open-files-limit is limited by the current limit of mysqld during SST. Seems like a bug.