resque-scheduler 4.2.0 not starting in BACKGROUND mode with BACKGROUND=yes

I am unable to start resque:scheduler process in the background by using the BACKGROUND=yes flag. The command which i am using is:
BACKGROUND=yes /usr/bin/bundle exec /usr/bin/rake environment resque:scheduler RAILS_ENV=development
resque:scheduler process starts successfully after running this but the rake process doesn't exit as it should after providing the BACKGROUND=yes flag. After the schedules get loaded, instead of running the scheduler in the background, jobs start getting enqueued in the foreground:

resque-scheduler: [INFO] [Rails:4] 2019-07-17T18:50:18+00:00: Schedules Loaded
resque-scheduler: [INFO] [Rails:4] 2019-07-17T18:49:06+00:00: queueing RequeueThrottledJob (requeue_throttled_job)

Checked this on a different terminal:

[ec2-user@ip-10-146-98-218 ~]$ ps aux | grep resque | grep scheduler
ec2-user 24515 14.7  1.2 860552 380748 ?       Sl   18:50   0:04 resque-scheduler-4.2.0[development]: Schedules Loaded

Strange thing to note here is that this issue doesn't appear when using rails3 application. The rake process exits and resque:scheduler starts running in the background as soon as the schedules get loaded.
These are the OS and package versions i'm using:

• OS - Amazon Linux 2
• resque:scheduler - 4.2.0
• ruby - 2.1.6
• rails - 4.2.11

Start by reproducing BACKGROUND=yes /usr/bin/bundle exec /usr/bin/rake environment resque:scheduler RAILS_ENV=development with resque-scheduler 4.2.0 on the reported Rails 4.2 setup, then compare it with the Rails 3 behavior described. Done means the scheduler continues in the background after schedules load and the invoking rake process exits.