With homeopathy you can at least hope for some placebo effect
Just to make it clear: it is undesirable to have formamide in any of the products but with the concentration we are talking about it is highly unlikely it will do any harm. The only concern for the formamide itself is its possible teratogenic effect but then again with the concentration and typical settings (ventilated room) the risk even for the product containing it is close to zero. Immediate toxicity of formamide is low. An adult would probably need to take a full glass of it (ca 200g) to have a good chance to die (ORL-RAT LD50 6000 mg / kg; IHL-RAT LC50 3900 mg / kg / 6h). For babies these Nos will be lower but likely within the same order of magnitude.
We have a baby, few months old playing on the mats from toysRus and soon we will move him to a different room. Probably the new mats will be bought again from the same source and what I am intending to do, is just to leave the mats spread in a well ventilated area (could be a balcony for example) for a week before moving them to the room. This is just in case and probably not even necessary. If the mats are not wrapped in a plastic package I would probably skip even this step. Formamide is a liquid, it evaporates. So longer you keep the mats less formamide is inside (if it was any).
Why were the authorities alerted in such cases like these in France? Because giving some specific circumstances it can be hazardous. I.e. somebody buys the mats with elevated levels of formamide and immediately puts it to a small, poorly ventilated space all over the floor and partly onto the walls.
A different example but similar area. Only few decades ago some lead based pigments were extremely popular for white permanent paints (indoor/outdoor). Many generations passed using these paints and apparently nothing catastrophic happened. But then again, there were very specific cases where use of such paint ended up fatal. One example was shown few months ago on the CI channel. A couple with a baby girl rented an old house in a rather poor aesthetic condition. The girl was usually playing outside, on some kind of veranda that was pained in white and the paint was peeling/chipping off. The girl, as many toddlers do took these pieces of paint and put them to her mouth playing with them. This continued for a number of months (IIRC) and slowly she started to get sick. Because nobody expected this kind of poisoning it took a long time to diagnose it and it was already too late.
So simply to get into any troubles with some "hidden" toxic materials it typically takes more than one factor. If the parents were a bit more responsible an not let her play alone for hours and put to her mouths whatever she wanted the tragedy was avoidable even with the lead based paints all around the place.