I've not had the survey yet but it is worrying that they go and arbitrarily break everything.
I don't think the current problem is necessarily the names, the problem is the descriptions/specifications of what they actually mean. This is self-evident in the fact that 'regular' caches are extremely rare. I definitely agree that nano sized caches need to be differentiated from 35mm caches as search techniques for the two of them are very different.
Below are what Groundspeak consider each size and what I'd propose - effectively it is mostly a case of shifting the definition down a category and making Micro be synomonous with nano.
Micro (XS):
Groundspeak def: Micro containers are less than 100 milliliters. They’re about the size of a film cannister, or smaller. They can hold a tiny logbook or log sheet. If a micro cache is less than 10 milliliters, it’s often called a nano cache
Proposed def: A micro cache is a nano cache/5mm tube etc. Sometimes you may only be able to sign initials on the log book.
Small (S):
Groundspeak def: Small containers are 100 milliliters to 1 liter. They’re about the size of a sandwich. They can hold a small logbook and trade items.
Proposed def: Small containers are generally unable to hold anything but the log book (and perhaps a short pencil). They are typically 35mm film canisters or magnetic key safes. The log book may be a roll/folded paper but large enough to sign and date fully.
Regular (M):
Groundspeak def: Regular containers are 1 to 20 liters. They’re about the size of a shoebox. Many of these caches are ammo cans.
Proposed def: Regular containers are large enough to hold a few trackables or swaps. They are typically clip-lock food boxes up to about 1 liter. The log book will more commonly be larger sheets or a notebook.
Large (L):
Groundspeak def: Large containers are more than 20 liters. Buckets, bins, or even railroad freight cars can be large containers.
Proposed def: Large containers can hold many or larger trackables/swaps. These include very large clip lock boxes, ammo boxes or even bigger containers. The log book will typically be a larger notebook.
Other (--):
Groundspeak def: Some containers just don't fit into size categories, like a magnetic sheet with a logbook attached. See the cache description for more information.
Proposed def: Some containers just don't fit into size categories, like a magnetic sheet with a logbook attached. See the cache description for more information.
Another approach is to keep the current definitions but insert nano as its own category at the start, this has the advantage of being less disruptive to current cache listings so may be preferable. Either way making changes is going to cause confusion and muck up some challenges.