The Venture Capital Working Group isn't claiming they weren't securities at launch. It's claiming that some of these tokens do not qualify as securities any longer.
This is in line with SEC Chairman Clayton's recent statement that tokens can start off as securities but become non-securities and vice versa [1].
In particular, refer to his example:
"If I have a laundry token for washing my clothes, that's not a security. But if I have a set of 10 laundry tokens and the laundromats are to be developed and those are offered to me as something I can use for the future and I'm buying them because I can sell them to next year's incoming class, that's a security. What we find in the regulatory world [is that] the use of a laundry token evolves over time. The use can evolve toward or away from a security."
In general, a solid framework for evaluating tokens that should count as securities vs. non-securities is the one put together by Coincenter, which is available here:
https://coincenter.org/entry/framework-for-securities-regula...
[1] https://coincenter.org/entry/sec-s-clayton-use-of-a-token-ca...