Hi Jayaprakash,
SAP Certification is a standard to gauge your knowledge level for any SAP tool / Product. It will help you understand the basics of HANA and so will the good training. If your concepts are clear, then you would be able to impress that upon anybody in a discussion. What your trainer mentioned might be right as the certification is not completely based on the study material. There could be some scenario based questions which you can answer based on the experience. But again different people have different experiences on the certification process and you can find multiple threads on the same on SCN.
HANA Application testing may not be very different from any other application testing, but the approach could be different. As you know HANA is continuously evolving, there could be many challenges as compared to any other application testing and there might be additional needs for the workarounds. I am sure your past background in QA will be considered for the suitable role in HANA development.
All the very best for your future in HANA 
.
Regards,
Ravi