SOLR-8381 made the _text_ field the default field for spellchecking for the basic_configs and data_driven_schema_configs example configsets. This is a copyField that gets all it's data from every other field in the index.
This field is also of text_general type, which has a default analysis chain that includes stopwords and synonyms. If someone has a large synonym list, perhaps with a lot of overlapping matches, this would cause spell checking to occur on every one of those terms. I recently saw a parsed query that looked like this:
Since we recommend that users use a lightly analyzed field for spell checking, using _text_ and text_general seems a problematic example for us to start people out with. The example above is a lot of extra work for little reason.
I'm not sure what a better field is - those two examples are minimal by design, and we can't be sure what field they might have in the index to make it work out of the box. However, perhaps we can consider a better field type?