Yes, BSPDN could gain ~10% block level density over FSPDN. Actually, this number is floating. Some case especially you use larger amount of HP/ UHP cell with dense power grid, this number can enlarge to 20%. But in most case, a ~10% gain in area will be mentioned and estimated. But this is only suit for same foundry comparison with FSPDN vs BSPDN. If you truely want to compare the block level density, then many detailed design rule flexibility and DTCO you need to be considered. Like N2 has short-tall cell offering which could gain extra PPA no matter for 15% performance gain on same area or transfer to same performance but x% area gain, and 18A do not offer this short-tall cell design until 14A. So how do you compared these block level density gain across different foundry?