If there is a sickness absence problem, then introducing disciplinaries once certain triggers are met is not unusual as a deterrent.
Bradford factor means it's not specifically based on number of days off, but also incidences, so if there are a lot of mysterious headaches and tummy upsets on Mondays and Fridays which the company views as suspicious or unnecessary, it might well be the best method to deal with it.
If there are people who currently view a set number of days off each year as kind of extra holiday, the fact that the Bradford factor is based on incidences might make it harder for them to do that.
I'm personally not a fan of automatic trigger systems of any kind for sickness absence management because they usually don't allow for discretion and can also mean line managers abdicating any kind of responsibility for monitoring or dealing with problem absence unless and until the 'system' tells them to do something.
I prefer to monitoring absence closely and individually, make sick pay discretionary so that it can be withheld if necessary, instigate return to work interviews every single time someone is absent and take a view in each individual case whether disciplinary action is the best way to reduce unnecessary or excessive sickness absence.
However in lots of companies having that level of discretion just isn't practical, and where there is a problem with people taking the p^$&, introducing triggers for disciplinaries can make people think twice.
Presumably if the triggers are resulting in a disciplinary interview and the company is convinced at the interview that all the absence incurred was genuine and necessary, there won't be any kind of warning or sanction imposed anyway?