Same issue here. Nexus 4 on Stock 4.4.4 Thankfully it appears support is right that the recipient does in fact receive a single message even though it looks like it sent as multiples from the device. To test this, I just sent myself a long text, which upon sending Airdroid looks like it split into 4 separate messages. Receiving the message however did yield a single message. See attached. Hopefully it's the case for my actual recipients. See attached screenshot. Glad to know it's a known issue at least.
UPDATE: The recipient does NOT actually always receive the broken message as a single long message. I just sent another test to a friend with an iPhone on iOS 8, and he said he received the message as 4 separate texts, exactly how it displayed on my end. Good to know it's a known issue with the single SMS app of 4.4, but for this app to tout these features, it needs to support them properly!