Sharepoint Online search result is different on filename search with and without asterisk wild character

I have two files, BTWaste.RN_SpecSheet.pdf and BTWasteCI.RN_SpecSheet.pdf, which are on same library, same folder and upload at the same time. I use “filename: btwaste” and “filename: btwaste*” to search. I expect result are the same for both search. Why only one file on search result for “filename: btwaste” searching?

I remove dot on file name, BTWasteRN_SpecSheet.pdf and BTWasteCIRN_SpecSheet.pdf, result is still the same.

With asterisk search result

Without asterisk search result