Lacking anything specific and clear cut; we do not question the judgement and authority of the KO here at AAP.

Note: I'm assuming BOSC = Base Operations Support Contract, but not sure.  I'm assuming SO's = Service Orders, but not sure. I won't venture a guess on FSC; that is most often Federal Supply Class in contracting. Final assumption is that the SOs are funded with O&M appropriations.

It is impossible for us to provide a specific answer to this question without knowing the terms and conditions of the BOSC contract and individual SO's.

The rationale could be labor law requirements, e.g. a new wage determination is required. But that could leave open the possibility of a modification increasing the labor rates.  Or, more probable, a fiscal law issue: if the SOs are longer than one calendar year and the services provided are severable (see FAR 32.703-3 and DFARS 232.703-3(b)) the period of performance cannot exceed one (1) year.