Very good question! I actually didn’t know it works without the dot. I usually put both because in other corpora the tags don’t work without both the dot and the asterisk.
Now, what I discovered though is that not adding the dot gives much fewer results:
[tag=”R.*”] gave me 335,222 hits
[tag=”R*”] gave me 203,447 hits
Is it a matter of quantity just? No, I examined the Frequency to see what “sub-tags” each search includes:
[tag=”R.*”] gives us a wider variety of adverb types e.g. RL (locative adverb), RG (degree adverbs), – see link
[tag=”R*”] gives us only RR (general adverbs) and RRR (comparative adverbs) – see link
So, I am assuming this would be the case for other searches without the dot – N.* will give you more types of nouns as opposed to N*
I hope this helps.