It certainly *could* be.

https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:53174778859588

https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:2818414600346806270

Start a fresh session and do a full refresh. As well db file seq read, check out the 'table fetch continued row' session statistic - if that's going up fast, then you are chaining, eg

-- 200 columns
SQL> create table T1 ( c1 int );

Table created.

SQL>
SQL> begin
  2  for i in 2 .. 200 loop
  3    execute immediate 'alter table T1 add c'||i||' int';
  4  end loop;
  5  end;
  6  /

PL/SQL procedure successfully completed.

SQL>
SQL> declare
  2    l_ins varchar2(32767) := 'insert into t1 values (';
  3  begin
  4  for i in 1 .. 200 loop
  5    l_ins := l_ins || i||',';
  6  end loop;
  7  execute immediate 'alter session set cursor_sharing = force';
  8  for i in 1 .. 1000 loop
  9  execute immediate rtrim(l_ins,',')||')';
 10  end loop;
 11  commit;
 12  end;
 13  /

PL/SQL procedure successfully completed.

SQL>
SQL> select st.value
  2  from v$statname s, v$sesstat st
  3  where st.STATISTIC# = s.STATISTIC#
  4  and st.sid = sys_context('USERENV','SID')
  5  and s.name = 'table fetch continued row';

     VALUE
----------
         0

SQL>
SQL> select count(c200)
  2  from t1;

COUNT(C200)
-----------
       1000

SQL>
SQL> select st.value
  2  from v$statname s, v$sesstat st
  3  where st.STATISTIC# = s.STATISTIC#
  4  and st.sid = sys_context('USERENV','SID')
  5  and s.name = 'table fetch continued row';

     VALUE
----------
         0

SQL>
SQL>

Compared to 400 columns

SQL> drop table T1 purge;

Table dropped.

SQL> create table T1 ( c1 int );

Table created.

SQL>
SQL> begin
  2  for i in 2 .. 400 loop
  3    execute immediate 'alter table T1 add c'||i||' int';
  4  end loop;
  5  end;
  6  /

PL/SQL procedure successfully completed.

SQL>
SQL> declare
  2    l_ins varchar2(32767) := 'insert into t1 values (';
  3  begin
  4  for i in 1 .. 400 loop
  5    l_ins := l_ins || i||',';
  6  end loop;
  7  execute immediate 'alter session set cursor_sharing = force';
  8  for i in 1 .. 1000 loop
  9  execute immediate rtrim(l_ins,',')||')';
 10  end loop;
 11  commit;
 12  end;
 13  /

PL/SQL procedure successfully completed.

SQL>
SQL> select st.value
  2  from v$statname s, v$sesstat st
  3  where st.STATISTIC# = s.STATISTIC#
  4  and st.sid = sys_context('USERENV','SID')
  5  and s.name = 'table fetch continued row';

     VALUE
----------
         0

SQL>
SQL> select count(c400)
  2  from t1;

COUNT(C400)
-----------
       1000

SQL>
SQL> select st.value
  2  from v$statname s, v$sesstat st
  3  where st.STATISTIC# = s.STATISTIC#
  4  and st.sid = sys_context('USERENV','SID')
  5  and s.name = 'table fetch continued row';

     VALUE
----------
       296

If you *really* need all those columns, then you can't really eliminate the issue altogether, but you can reduce its impact as much as possible by putting the "most-nullable" columns past the 255 mark.

It's only when columns 256 onwards *contain* data that we need to do the piecewise fetch.