In general A2P messages are subjected to harsh anti-spam filters. SMS spam filters work similar to email spam filters - i.e. they use various Bayesian rules to calculate spam score and classify the message as spam if that score is above threshold.

In addition, SMS filters are more strict than email filters - because they have a lot less text to work with and also SMS spam is more annoying than email spam. The downside is that there are more false positives than in case of emails.

So it is quite possible that your message exceeded the threshold with "Verizon" in it, but was just below the threshold without "Verizon".