Cut a hole in the sides of the tent and install the vent cover. It's similar to what
@Gemtree is recommending.
There "has" to be a…
[time passes]
This is the tent you've got:
View attachment 5478634
You're fine. The tent is
not air tight. Even if you close the flaps and push the velcro tight, air is going to get in the tent.
Just leave them loose and you'll be fine. You won't get light in there unless you shine a flash light in there.
There's a huge mystery about plants getting "too much light". The "science says" it's got to be bright enough to read a large print newspaper before there will be an issue. Think about how much light there is under a full moon. It's quite bright for humans but not near enough to cause problems for plants.
Your tent is fine.
The answer to the title of the thread is "no, tent flaps are not a light threat"