Congrats. And yes, follow the instructions and you'll get it. I don't understand why people are trying to do everything their own way and make it difficult...
Yes, in that case the person received a multiple entry right away from abroad. However, when renewing with immigration (after one year), you'll need to request for a multiple entry and most likely wait until the initial renewal is granted before applying for it at an extra fee.
You'll need to prove you're still in Vietnam... They want to see any proof with a very recent date like a purchase bill or others. You're the second person posting about it here. It's now getting stricter to make sure people remain in Vietnam until approved.
All these "anecdotes" don’t change much about the situation. Most visa holders make it through without any issues (as they are fulfilling their visas purposes), while some may be further questioned. The frequency of this can vary depending on crackdowns or the government’s intention to attract more visitors. It has always been this way, even before the DTV, and that’s exactly what immigration is there for.
Please stop listening to the so-called 'Months in Thailand Experts' who claim the DTV is a VIP lane with a red carpet; it’s not. Immigration is simply doing its job, just like in any other country. As mentioned, you have a long history of abusing tourist stamps and chose the easiest and cheapest route (medical) to remain in Thailand. Their questions highlight that the purpose of your visa matters. If you're holding a DTV for medical reasons, you're expected to fulfill those conditions. That’s something many people still fail to understand.