ERUDIO student loans help

I just received a strange letter from them. My 25 year sentence is up in Oct 2020. They wrote to me saying that on this date they would write off the remaining money that I would have owed. From now to this date I would make 2500 in payments but if I pay the loan off now I can do so for 2400. I'm not sure why they would do this as saving 100 pounds isn't that big of a deal so not sure of their incentive. Also they claim that if I take them up on their offer it may prevent me getting any student loans in the future. By that I take it they will report to credit rating agencies as debt not fully paid. Again I suspect they will do that in 2020 even though the terms of the loan have never been breached. Has anyone received a similar offer and has any insight as to their motivation?

Pinch of salt territory here:

Forum member anna2007 previously did some sterling work in this area and FOI'd the calculation that's used to generate the deferment threshold. As a low-posting user, I'm unable to link to it (may be able to PM it?), but I plugged in the ONS numbers for 2018-19, and the threshold came out as £30,562. Rounding errors may plus or minus a tenner; methodology errors may minus several thousand...

Calculation details (adapted from the earlier-mentioned FOI calc, using up-to-date ONS data) for the sceptical:

1) Mean gross weekly earnings from the 2017 Annual Survey of Hours and Earnings (ASHE), covers GB full-time employees and relates to April 2017: £662.50
2) Apr 2017 Annual Mean Earnings: £662.50 x 52 = £34,450
3) Earnings growth to Apr 2018, measured by Average Weekly Earnings (AWE): 4) Estimate of Apr 2018 Annual Mean Earnings: £35,300.91
5) Projected Annual Mean Earnings in Jan 2019: £35,300.91 x (1 + 2.47/100 x 0.75) = £35,954.86
6) Annual deferment threshold: £35,954.86 x 0.85 = £30,561.63