Yes, its true. Units 1 to 7, are considered mandatory and are considered as external examinations, so if you don't gain a pass or higher for these units, you will fail your entire grade. You can work this out by using the online BTEC grade calculator - Use the link below to calculate your grade(s) for btechttps://qualifications.pearson.com/content/dam/pdf/Support/Understanding marks and grades/BTEC_Nationals_2016_2018_Grade_Calculator_2018_2019_v3.xlsm