Long time since I've been on this forum!
A similar issue as here:
Seems to have persisted into verson 19.2
Here's a Debug excerpt from v5.1.0.x on the left and from the latest v19.2 on the right on the same call:
apex_util.set_session_max_idle_seconds( p_seconds => app_standard.c_ui_idle_timeout_secs , p_scope => 'GLOBAL' );
note: "app_standard.c_ui_idle_timeout_secs is just a constant:
c_ui_idle_timeout_secs CONSTANT PLS_INTEGER := 3600;
It looks to me like there used to be a routine to handle this but it's been lost in upgrade work somewhere between 5.1 and 18.1