If I uncheck "Available For Tagging" from a global termset can I still access it programmatically?

If I uncheck "Available For Tagging" from a global termset can I still access it programmatically? The answer would appear to be "No". I have a console app that uses 

TaxonomySession session = new TaxonomySession(site, true);
var termStore = session.TermStores[0];
termStore.UpdateCache();
var group = GetTaxonomyGroupByName(termStore.Groups, "Global Termsets");
TermSet globalTermSet = group.TermSets.FirstOrDefault<TermSet>(e => e.Name.Equals("My termset", StringComparison.CurrentCultureIgnoreCase));

OR

TermSet gts = group.TermSets["My termset"];

If I uncheck "Available for Tagging" this this fails. When I re-select "Available for Tagging", it works.

Obviously, this is the way SP is designed (I think) but my question is why? I don't want my navigation termset being used for tagging. I have a different termset for that. This suggests that tagging also controls api visibility to the termset. Is this something that other experienced developers can comment on?

Thanks!