As of now, no special round or spot round has been declared by IIT BHU for 2025 admissions—neither B.Tech nor M.Tech. The admissions are strictly happening through the regular process: B.Tech: through JEE Advanced + JoSAA counselling M.Tech: through GATE + COAP (with multiple rounds of offers) There is no mention of any spot round independently on the official schedule or admission website. If at all they intend to hold one later (which is rare), it'll be announced officially on their admission website. But as a suggestion, do not anticipate a spot round. Keep checking the official IIT BHU admission portal from time to time in case any update comes.
There is no special/spot round for seat allocation to IITs during the counseling process. Such a round is, however, organized by the CSAB to allot the vacant seats in NITs. For the IITs, NITs, and GFTIs, the JOSAA conducts the counseling in 7 rounds. The reason behind the 7 round counseling is to make sure seats won't remain vacant. In the counseling, a large number of rounds ensure that most of the students' choices are considered, and minimum seats in these educational institutes remain vacant. The special/spot round is constituted only for NITs owing to the reason that NITs have more number of vacant seats as compared to the IITs, which would incur losses to them. Also, as this process requires a lot of resources, it is conducted only for NITs.