When we discard an element, we want to make sure that the new state is not corrupted by previous user operations. In our case, we possibly had a limit and an offset values modified by the user. This could lead to unpleasant situations, with incorrect data displayed on the form view. Note that this actually fixes a new bug introduced by commit https://github.com/odoo/odoo/commit/e7fab234201e357da52c3576ad2e8fc9ceee9359 (this is the commit that introduces the tempLimitIncrement attribute)