It's not a big deal. I never noticed fluctuations in my FICO scores as a result of Synchrony doing precisely this: not generating a statement and therefore not reporting unless there was a balance.
If it's ND (no data) you still get the pretty OK later when it next reports. I've gone a year without using my Wally card, and it still looks like any other tradeline now from a FICO perspective.
To be fair if you have like no other tradelines besides these cards, and you don't have any activity in the last six months, then you might temporarily lose your FICO score altogether until you get another trigger, but this is such a ridiculous corner case that it's not a big deal as everyone should have at a non-store card tradeline somewhere on their report.
It's possible though on more of an edge case scenario that if the bulk of your tradelines were inactive by the six month rule, they might not get counted and suddenly you might get some impact from having very little reporting or maybe your ratio of non-zero balances getting non-trivially out of whack as a result... though with my having at least 4 cards in addition to the Wally card, it wasn't even a rounding error. There's some other esoteric issues but it's simple: just go get a credit card from a bank or your local CU and go on with life.
