Every airline I've flown with had X-wind landing limits for F/O's. They were all less than max demonstrated. Common was newbies 15kts and experienced F/O's 2/3rds of any runway limitations including gusts.
Except for the newbie restriction, we have no x-wind restrictions for our experienced first officers. And rightly so. Our first officers are selected and trained to be captains. If I have a heart attack, should my first officer not be able to land if the x-wind is inside the recommended aircraft limit?
When he changes to the left seat, do you expect him to suddenly be able to perform max x-wind landings after years of not doing any?