Yep, many employers have formal sickness absence monitoring processes nowadays. In my experience (at a previous place of work) this worked very effectively and definitely put out the message to several malingers that "we're on to you" which resulted in said employees either voluntarily leaving the organisation or improving their attendance.
I think that, if administered and delivered correctly by good HR personnel, such schemes are worthwhile. I had no worries about having to attend a formal interview having had 3 periods of sickness absence within a year (foot operation, RAI treatment to thyroid and then breast cancer treatment). All sizeable chunks of absence. The HR officer stressed that the formal interview was in no way a disciplinary matter - he was extremely supportive and sought to gain assurance from me that everything was being done by Occy Health and managers to enable my return to work and make reasonable adjustments. This, by the way, was at a place of work which didn't formally recognise unions.
If someone is a malingerer they can rightly be intimidated by having their sickness absence monitored, if someone is a conscientious employee with genuine reasons for absence (whether self- or doctor-certified) they should have no need to be concerned.