Hello Tom
thank you for your feedback.
It seems i do not understand the workflow: you want to open file with crytomatte and it opens slower (what is logical, since many extra layers need to be rendered in PS). And because it is slower, you switch to V1, which can not load Cryptomatte layers at all (which is faster, because there is no support in V1 for Crytomatte). But you can not then open Crytpomatte info with V1. What did i misunderstand?
Why do not open a file with Crytomatte toggle checker OFF? In this case, Cryptomatte wont be included in the loading process?
Second and your correct observation:
V2 has indeed a different loader procedure then the V1 - we have had two years time to discuss the features with thousands of cg studios and best artists: they main problem was the memory consumption. Therefore we have rewritten the core so one can load gigantic data without crashing computer by compensating it through optimizing memory segments. This causes some slow down in some cases, but it guarantees the image loading.
The studios told us they do not give a damn about time (5 seconds or 7 seconds, 40 seconds or 46 seconds) when they can not load the image because there is no enough memory to read and write it as EXR. There is a case in my video-presentation where i load 4 GB file with 30 layers in V2 in 35 seconds. It is mainly slowed down by the speed of my SSD. The 5 seconds lost are... irrelevant. The advantage was i was able to load it in 32GB Ram machine, which did not work well with V1.
So, long explanation for a simple sentence: maybe turning off Crytomatte, if you do not need it, can help you.
Finally, Exr-IO V1 is obsolete, but still a great piece of software even now in 2019.
ps. One more thing: if you drop EXR from Vray, Arnold etc with Cryptomatte-Node, unsorted, unclassified, where each grass blade get one layer, it will generate huge amount of unnecessary layers. Photoshop has the limitation of 8000 layers. My opinion is, although i get sometimes Matte-plates from Hollywood guys with 100+ layers, that one can not work reasonably in PS with 300+ layers. If you have 1000 layers, you did something wrong. From that point on it is a mess.
You do not need for each object a mask. Organize them in layers or user-properties: Vray has such a beautiful options for a disciplined workflow, it is amazing to see that even the most complex scene can have at the end only 30 entities
thanks
best regards