I mostly agree, but the scale of what Twitter is doing technically is very different.
Network size is not as important as how messages are distributed within it. Whereas most WhatsApp messages are one to one, on Twitter they're almost always one-to-very-many.
If 10000 Twitter users with 1000 followers each send a tweet, that's 10000000 messages hitting queues. 10000 WhatsApp users sending a single message each are likely to result in 10000-20000 messages (sometimes people have group conversations).
Network size is not as important as how messages are distributed within it. Whereas most WhatsApp messages are one to one, on Twitter they're almost always one-to-very-many.
If 10000 Twitter users with 1000 followers each send a tweet, that's 10000000 messages hitting queues. 10000 WhatsApp users sending a single message each are likely to result in 10000-20000 messages (sometimes people have group conversations).