Hydrangea blooms do not come in true red so take descriptions that mention 'red' with a grain of salt. Typically such shrubs just turn a shade of dark or magenta pink instead. This 'Red' may resist turning blue like other similar ones in acidic soil ... and could even turn purple at very low, soil pH acidic levels... you just have to try and see what happens when the roots "leave" the potting soil after you plant it into your garden soil. Whatever bloom color happens will depend on your soil pH, amount of aluminum & other minerals in the soil, genetics, weather, amount of sun, etc.

The patent does not say what color it will get in acidic soil:

https://patents.google.com/patent/USPP18450P2/en?q=Hydrangea&q=macrophylla+%27Maltisse%27&oq=Hydrangea+macrophylla+%27Maltisse%27

Thus I would assume that it will resist turning blue and do a shade of pink or maybe even purple.

I really dislike how nurseries misrepresent hydrangea color and are not truthful in regards to the effects of soil pH.

I hear you. Same thing happens when they name something "Blue this or that" and it is purple-ish. By the way, I just finished a scan of references to this Red in the forum and found some critics saying it did not bloom well for them. Do a forum search using "Hydrangea macrophylla Maltisse" and review the various posts.

Thank you Luis