Hmmm. This seems to be a rehash of the graphs they used to publish. I have a problem with their assertion that Delta 100 has the same reciprocity curve as FP4, given they are two different grain structures.
These tables or in this case Mathematical Formula are very misleading because it depends also on the lighting conditions, colour temperature/time of day etc.
Experience or testing is the only true way forward. I tested Fomapan 100 & 200 a few years ago for lighting I'd shoot in and found Foma's own data was way too pessimistic by a long way, but then I was shooting at half box speed with reduced development.
Joanna, I wouldn't worry about grain structure, actual response is more important.
Reciprocity isn't a big issue it's just something quite simple that you take into account like bellows factor, filter factor etc.
In over 50 years shooting film it's not been something that has been a problem or hindered me in get the shots I've wanted.
My main LF films are Delta 100 with HP5 for hand-held work. With long exposures I'd be using a tripod so using Delta 100 (I often carry both films). I wouldn't chose my film based on published Reciprocity characteristics if I did I'd never use Fomapan 100 or 200, my own practical testing showed me Foma's data was way out in low light levels, nowhere even close to as bad as their Datasheets.