The percent different between 1.3% and 0.93% is quite large, around 30%. That's what counts, not the difference of those two percentages.
TBN of 11 is higher than most oils start with these days. There are some with more. One example: M1 0W-40 TBN is around 12 IIRC.
Downsides to 1.3% ash? I can't say for certain. Different engines have difference "tolerance" for ash...in the piston/rings/combustion chamber regions. It's not going to make really bad things happen. At worst, it won't be ideal. At best, those regions will get cleaner in terms of carbon and varnish. You'll have to try it and see what you think of the oil.