Assuming I still use this exchange, this email would have been a warning sign for me and I would have stayed away from the exchange till further notice, at least when I know that everything has become functional again because this email seems like downgrading their services.
To maintain just the mobile apps will be easy than to mention them along with the website. I do not think what they did is wrong because everyone are now using mobile phone. Also, it is possible that they check people's means of visiting their exchange and noticed mostly from mobile devices. Although, maybe you are right, but I do not think so for now.
Now this agree with what I said before about our government banning access to websites of exchanges. I knew that started from that period they accused cryptocurrency of causing the crash of the Naira, one of the funniest and dumbest statement of those that we call leaders. I think it is has become obvious now that their decision to banned exchange websites did not yield any results because it did not stop people from using those exchanges neither does it slow down the adoption of cryptocurrency in Nigeria. I really know who is advising our government but the fact remains that those advisers are doing terrible job especially with cryptocurrency.