As per EMA guideline in following scenarios lower strength can consider:
1. If the highest strength cannot be administered to healthy volunteers for safety/tolerability reasons. for example: antipsychotic drugs
2. If the pharmacokinetics of the drug is non linear, that means AUC doesn’t increase in proportion to dose administered, and if there is less than proportional increase in AUC due to saturation of uptake mechanism and there are no excipients that alter GI motility or transport proteins.
Do let me know if you know any other situations when BE is acceptable only on the lower strength.
Second scenario is a little complicated to understand, just do a little research to understand it better.