BPP 92 Tryde Co

Hello Sir, Hope you are well. When i don't understand the answers provided in the BPP book, I look the question up on opentuition to see if you have explained it before, however i did find the question and answer but the answer that was correct at the time is now different? I couldn't reply on the previous forum, but here is the link: https://opentuition.com/topic/question-208/. The answers are 6.20 semi strong and 6 strong, these answers are also confirmed on the ACCA website under the examiners report. However my BPP text book afters say: 6.05 semi strong, 6 strong and 6.20 strong (not sure why there is 3 answers when they ask for 2, but assuming they will give either or?). Is there a reason the answers have changed as the 6.20 has gone from semi strong to strong? or is the answer in BPP book wrong? Thank you in advance.