Anybody who has a K-1 coming from a company or has brokerage company 1099's should wait until absolutely April 1 or even later to file their income taxes. Doing that before April 1 will most assuredly guarantee an amended return. What's the rush? I doubt that you are getting EITC or some other refundable credit. And if you are expecting a refund, your CPA accountant is having you make too much of estimated payments or you are having too much withholding taken out at work.
complain loudly and frequently to Blackstone that they need to get their act together and send final K1's to investors in a timely manner, just like real grownup companies do. There's no excuse for this!