Accurate enough for who? It wouldn’t be accurate enough for me. And it certainly wouldn’t be accurate enough for the consumer who you described as expecting that estimate to match reality. And worst of all, it wouldn’t be enough for any consumer protection agencies or remedies. So many assumptions would have to be made based on factors entirely outside of their control in order to sell to you based on your file download speed. And if you allow them to sell you a product based on assumptions of things outside of their control, then you then have to recourse to hold them accountable. I don’t want companies to sell me a product based on a number offered over a shrug. I want a number I can measure against what I’m getting.
Transmission rate is the only metric with any meaning in this context, because the transmission rate is the product they’re selling to you. The overprovisioning and etc is actually accounted for in the transmission rate they’re selling you. Thats why they almost always overprovision your connect based on what you’re paying for.