type="post" / field_type="checkbox_list" returns only single id

I setup a field of type "post" and field_type="checkbox_list" in order to select multiple posts.

https://pastebin.com/TLKCfN5x

When saving the post, the backend shows the checked posts correctly.

But when getting the data on the frontend:

$tour_ids = rwmb_meta( 'prefix_fp_tours' );

My variable $tour_ids only returns a single id.

Tried WP's function:

$tour_ids = get_post_meta( get_the_ID(), 'prefix_fp_tours', false );

and here I get an array of ids.