I'd love to know how the two recordings are made. Are they done separately? For example, the normal speed sounds like "Gaeth hi" but the slow one is "Gaeth e". needless to say, I got it "wrong".
It is perhaps misleading to call them 'recordings'. They are generated by using text-to-speech (TTS) software - there is a general discussion topic about where to generate your own short speech examples using similar or identical voices.
In this example, the gaeth e ei may well sound very close to gaeth hi ei unless you have had a chance to listen to natural Welsh more often. If you hunt around the web you should be able to find examples of Welsh speech with accurate Welsh sub-titles or an available text - songs with lyrics are a good example to look out for, or poetry readings.
An example, Coffi Du, here (with a strong north-west Wales accent and dialect). Trons Dy Dad is another well-known one by the same band. Kizzy will probably have some sub-titled tracks somewhere, too.
No it's definitely that the TTS is getting it wrong. The aspiration of hi is really clear :-(