custom fields in hook_civicrm_pre' $params have an extra "_-1" suffix

Question

On my latest Civi 5.37.2 the params array passed to hook_civicrm_pre looks like:

Array
(
    [hidden_custom] => 1
    [hidden_custom_group_count] => Array
        (
            [] => 1
        )
    [custom_395_-1] =>          <-------- Spooky appdx
    [custom_463_-1] => 1000     <-------- Spooky appdx
 [...]

This happens when adding a new activity to a case. hook_civicrm_customPre works in other cases but it is not fired here. So it seems, there is no hook to get a sane custom_<fieldid> param prior saving to db.

Answer 1

Converted comment to answer:

I think it's always been like this? And for editing an existing one it's not -1 it's the autoincrement id in the customvalue table.