That's right. The first limitation I've come across in the blog is that the tag/label field has a maximum of 200 hundred characters only! Google doesn't anticipate that someone would use cross-referencing to the extent that I do.
So what's the way forward?
It's to prioritise the index/concept numbers (e.g. 01.02.3) over the concept names (e.g. Concept: frame shape). The concept numbers will be tagged as completely as possible; followed by the concepts by name, in relevance order. Not ideal, but the small 'bright side' is that the limit forces me to identify the priority order of concepts.