You are on to the correct interpretation.
The key is trajectory. THe other is to look at the over-sample of democRATS in the polls. most are +10% democRAT so they are not reliable in and of themselves, but if we see an upward trajectory for Trump with the built in biases, then Trump may very well win it.
Furthermore only 8% are willing to be polled. Conservatives distrust pollers and thus get underrepresented.