This is unrelated to net neutrality.
you're correct that taxation of internet streaming content by the government is not what is conventionally meant by net neutrality.
however, I do think that taxation is highly relevant for issues of economic fairness. is Pennsylvania subjecting streaming services to a different level of taxation is their non-streaming competitors? that would be economically unfair in a similar way that non-neutral network access would be unfair.
The first sentence of the article (emphasis mine): "Pennsylvania has joined several states in enacting a tax on digital streaming and download services."
Unless you can think of a competitor that offers neither streams nor downloads, no, they're not.
From Pa. Code § 9.2. Sales and use tax changes:
(2) Pay television. Pay television except for ‘‘minimum pay television’’ is taxable. This includes anything charged to a customer for a service other than minimum pay television service. For example, if a cable television customer purchases basic service and in addition purchases a ‘‘pay’’ channel, tax is owed on the price charged for the ‘‘pay’’ channel. Installation and repair service for pay television with the exception of minimum pay television also is subject to tax.