It is an issue. Suppose 1 share of holdco is worth one share of SFB because holdco is doing nothing else. So today you have say 100 shares. After listing of SFB, you will have 60 shares directly of SFB and your holdco shares will be equal to 40 SFB shares BUT with a discount. So new valuation would be 60 SFB shares + 40 SFB share with 20%-80% discount.
Another case is if they have to IPO the SFB and decide not to give any shares to holdco investors. Then holdco guys will get only cash from sale of 60% which again will be valued at less than cash value.
EDIT: A lot of people are comparing it with IDFC and IDFC Bank. In that case, IDFC had many other businesses. Ujjivan/Equitas holdco are doing nothing else and won’t do anything else as management has clarified. So there really is no need for them to exist separately. Why would you run a company to hold shares of another company and do all the paperwork and expense? So if holdco and SFB merge at a later date, in that case there will be no impact on shareholders of today.