She did her work as her manager had instructed. 她按经理的指示干了自己的工作。

= She did her work as her manager had instructed that she should.

as引导方式状语从句（比较分句的一种），as为比较代词，替代动宾结构do her work。所以从句should后不可再用实意动词。

She arrived at 10 o' clock as instructed. 她按指示于十点到达。

= She arrived at 10 o' clock as it was instructed that she should.

as引导方式状语从句（比较分句的一种），as为比较代词，替代动状结构arrived at 10 o' clock。所以从句should后不可再用实意动词。

以上二句中，as从句均表示，主语做的事与要求她做的事是一致的。（二件事一致——比较分句的本质意义。）