Because there are many kinds of bonds, the main bodies eligible to issue bonds in China are the government, financial institutions, companies and enterprises. The bonds issued by these entities are legal.
The securities companies you mentioned belong to financial institutions, and the short-term financing bonds issued by them are legal and belong to corporate bonds in bonds.
This is my opinion, please forgive me if I am wrong. You can also correct my mistake. I'd like to talk to you about finance.