SS WH, for instance, if someone earned enough to go over the limit at one job, then get/have another job in the same year, the second employer MUST still WH SS based on their own YTD for the employee. It is up to the employee to get credit/reimbursed. Meaning there is nothing an employee can say to employer 2 to have them stop SS WH even if they have gone over the required amount for the year because of other employment.
I suspect retirement is similar in that one employer has no responsibility or ability to monitor any other employer, so in the case of retirement, if the plans allow, the employee can elect to manage their contributions/matches in such a way as to not go over the limit in total. If the employee goes over the limit, it is up to the employee to handle the issue, not the employers. Of course, the employee would be wise to contribute as much as they can if one has more matching funds, or to split it evenly if both have similar matching funds (as a kindness to both employers).