That’s not exactly true, you’ll get a MA unless this situation applies:

The placeholder code “UA” will be used instead of “MA” under the following circumstances:
a. The use of the “UA” code shall be limited to cases where the Company is contacting pilots in reverse order of seniority on a day off, to fill open time in accordance with Section 11.I.1.e-f.
b. When a pilot is positively notified of a junior man assignment by the Company per Section 11.I.1.e-f. and the pilot is unable to accept this assignment due to personal reasons, the Company will use the absence code “UA” in his planned absence record (HI10 or *4) as a placeholder.
c. Only the Domicile Chief Pilot, in consult with the pilot, will be permitted to remove or replace the “UA” code.

So basically only if they call you at home on your day off.