Plagiarism checking or chequing?
There is no reason to suspect that this is an essay harvesting exercise, as is the case with other 'checking services'. The submitted essays are not added to the Global database, students' subsequent submissions are not then compared with the 'original', and no such matches are flagged-up.
Should the 200+ UK HE customers aim to address this? Are HEs driving their students to this by not supporting them adequately with academic skills support?