Inquiry about tags with `"^{}" characters`

[seoha0821]

git ls-remote --tags --sort v:refname https://github.com/PyCQA/isort
When the above command was executed in Git Bash, it was output as shown below.

$ git ls-remote --tags --sort v:refname https://github.com/PyCQA/isort
83f40192d25692dfc36930df9908962903580c06        refs/tags/0.0.9
︙
f13b010477f777d33649cd6aa838b4ce8e148db2        refs/tags/4.3.7
234c539c98a9ab6b657563bcbf1f95f649b2a3ac        refs/tags/4.3.7^{}
7211675f1195c2241824e402251af943c97a406e        refs/tags/4.3.8
bfabca6bd1c178cda98de41149f55933cfe37e65        refs/tags/4.3.8^{}
c4a1c105add8eeeeb30baf35c567c6671b8741f4        refs/tags/4.3.9
b15e5903bcf1926c06b37403d7b9047c9559baf3        refs/tags/4.3.10
f6ff653fbf149b67cef1e553940b788a9afa685e        refs/tags/4.3.10^{}
︙
98390f5fde8f904f16a4e290a2aabed80d0951dc        refs/tags/5.11.4^{}
6dfb85379703e7e99834ffc9dc9c05942a202532        refs/tags/5.11.5
dbf82f2dd09ae41d9355bcd7ab69187a19e6bf2f        refs/tags/5.12.0
e44834b7b294701f596c9118d6c370f86671a50d        refs/tags/5.12.0^{}
17102ef8212398008c99671f3230a18015bba51f        refs/tags/5.13.0
9f7e0e51c6ab6c58695cdd3151fb886e287a67bd        refs/tags/5.13.0^{}
395ffd2753d847d4bf16909603466c2aa446fc44        refs/tags/5.13.1
643d9c478d597bdb9703ee0abed9919df336e3bd        refs/tags/5.13.1^{}
c235f5e450b4b84e58d114ed4c589cbf454175a3        refs/tags/5.13.2
c655831799765e9593989ee12faba13b6ca391a5        refs/tags/5.13.2^{}
0a0b7a830386ba6a31c2ec8316849ae4d1b8240d        refs/tags/6.0.0
c8ab4a5b21bac924d106e3103dd7c979fdd0f9bc        refs/tags/6.0.1
dbfeff978be405f59704097cf11c59110a08e67b        refs/tags/v5.11.3
6c83bcc7b6316b186c4ffb2b445cccc0ce853958        refs/tags/v5.11.3^{}

I'm not sure if it came out the same before, but there is a tag with the letter "^{}".
Can you check on this part?
And I would appreciate it if you could let me know the cause of the occurrence