MGMAT SC Guide Doubt

Hi Folks,

Below has been mentioned in MGMAT SC guide

"Note that the verb TO BE does not have to be part of a linking verb phrase. The verb to be
also forms the progressive tenses (I am watering the plants) and the passive voice (The plants
were watered last night). Do not look for parallelism in these uses of be."

How to generalize "THESE" in RED

So How we can segregate where to make the elements parallel when linking verbs are involved and where there is no need for checking parallelism.

Plz Advise

Rgds,
TGC!