If you raise $100M you have to put $100M to work or you'll hear constant shit from your board over it.
If they raised $160M they're going to spend $160M on something. My guess would be a lot of enterprise features and product integrations.
With x% high enough, sure, you can get VC money without too many strings. (Also, reading the Series B post, they were planning to invest - just in organic growth instead of the usual growth hacking)
And if you read the Series C post, you'd know what they're spending on - GPU (and general) cloud interconnectivity.
There's really not much need to guess, Tailscale's financing announcements are about as open as you can get.
The. fine. article. seems. to. say. lots. of. companies. are. using. Tailscale. to. connect. to. servers. with. GPUs. -- nothing. in. that. implies. that. Tailscale. would. own. the. GPUs.
Besides my joke, you are bang on, nothing implies needing to buy GPUs and based on my knowledge of their product/the space, absolutely no reason to.
What matters is why. Is it because growth is so bonkers that your burn stays minimal/zero despite increasing costs? Or is it because you don't spend anything and thus can get by with stable revenue. VCs are very happy with the first, less so with the second.
VCs would always prefer you get to megascale with less money - the less you raise, the less they get diluted.
of COURSE you can raise money and not use it.