When you change the DATESTYLE= option to DMY to read date fields correctly and you set the value of USEDATESTYLE=YES (which is needed in order for the DATESTYLE= option to be honored), a quoted string is read as a date and not a character field. 

For example, the following sample data causes the issue:

range,startdt,amt,amt2,startdt2
"21-27",12-12-22,12345.5,22345.5,12/12/2022

Here is the PROC IMPORT code:

options datestyle="dmy"; 
   proc import datafile='c:\temp\sample.csv' out=sample  dbms=csv replace; 
  run; 

After you set the USEDATESTYLE= to YES in the SAS Registry, as shown in the image below, the issue occurs:

The RANGE variable is read as a SAS date using the DDMMYYw. Informat instead of a character variable using the $w. Informat. As a result, an invalid data message similar to the following occurs in the SAS log:

NOTE: Invalid data for range in line 2 1-5.
RULE:     ----+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+---
2         "21-27",12-12-22,12345.5,22345.5,12/12/2022 43
range=. startdt=12/12/22 amt=12345.5 amt2=22345.5 startdt2=12/12/2022 _ERROR_=1 _N_=1

Workaround

If you use the IMPORT procedure in SAS to read an external file, complete one of the following workarounds to circumvent the issue:

• Recall the generated DATA step code from the SAS log if you are running SAS interactively. Modify the INFORMAT and FORMAT statements for the variable that was read incorrectly by changing the INFORMAT and FORMAT to $CHARw. in both statements and add a $ after the variable in the INPUT statement. You can recall the generated DATA step code after running PROC IMPORT by selecting Run ► Recall Last Submit from the SAS menu bar.
• Use a DATA step with the INFILE and INPUT statements to read the external file instead of using the IMPORT procedure.