Redis Cache does not respect WP_REDIS_HOST

In my wp-config.php file I have defined following settings:

define('WP_REDIS_PORT', 6379);
define('WP_REDIS_HOST', 'redis-app.redis-namespace.svc.cluster.local');
define('WP_CACHE_KEY_SALT', 'H1KAO39122');

I made double sure, that the Redis server is accessible using curl command:

curl redis-app.redis-namespace.svc.cluster.local:6379

The Redis server did react on this request:
1606752254.891864 [0 10.0.0.158:42710] "Host:" "redis-app.redis-namespace.svc.cluster.local:6379"

Still, the plugin is unable to connect with Redis server.
Whenever I do use:

Enable Object Cache button,

I constantly have “Not connected” status.

Diagnostics:

Status: Not connected
Client: 
Drop-in: Valid
Disabled: No
Filesystem: Working
Ping: 
Errors: [
    "Connection refused [tcp:\/\/127.0.0.1:6379]"
]
PhpRedis: Not loaded
Predis: 1.1.6
Credis: Not loaded
PHP Version: 7.2.24
Plugin Version: 2.0.15
Redis Version: Unknown
Multisite: No
Global Prefix: "sm246_"
Blog Prefix: "sm246_"
WP_REDIS_HOST: "redis-app.redis-namespace.svc.cluster.local"
WP_REDIS_PORT: 6379

Honestly speaking, I have an impression, that WP does not respect WP_REDIS_HOST variable and still tries to connect with the default host:port

"Connection refused [tcp:\/\/127.0.0.1:6379]"