My understanding is a biscuit's primary purpose is to hold the timber perfectly in position as the glue dries which often takes days even with glue that "dries" in minutes.
For example I have a tube of "instant" liquid nails that advertises a strong hold after just 2 seconds but requires a full week to reach it's full strength potential.
Any movement during that week massively reduces the strength of the glue bond. I've even seen joints separate entirely due to expansion/contraction of the timber as it adjusts to the ambient humidity.
A biscuit only needs to be strong enough to hold the timber in position for an hour or a few days after which the glue alone will be strong enough to hold the joint together (dowels or screws or brad nails or clamps or a spline joint would be just as effective, but biscuits can be quicker/easier than any of those).
Many glues are so strong even with a sledge hammer you'll struggle to separate an edge joint. The timber will splinter and snap while the joint holds strong.
These things obviously vary depending on the timber and glue being used as well as surface preparation (sanding/cleaning/etc). If you're worried your joint won't be strong enough, test it out with a scrap piece of timber. If it doesn't work, I suspect you're doing something else wrong (for example some biscuit jointers cut the slot too big the biscuit should need a light taps with a hammer force it into the hole).