Who knew. So a rear on the front should be run backwards due to the splice.
Then rain dispersal becomes and issue.
The OP says he is going to run in slop. If it is thick slop, then a different tire with a different tread pattern would be best. You can ride on gravel roads with regular street tires, but it gets tiring very quick. Trials Universal tires, or their modern equivalents would be much better, as Rollin demonstrates.
For the cost of a new tire, I would use the most appropriate tire for the job.
UK
Yes.
Have not seen it lately but in the mid 1980's EVERY Dunlop DOT approved rear race tire (running on the rear), that I saw, at the track had the splice showing some separation.
The Dunlop guy claimed they were safe to use so we ran them anyway, that day.
None came apart that I know of and a lot of guys kept using them.
I changed to Metzeler before the next race weekend... Never saw the splice on a Metz.
Those were the old bias tires of the day but tires today still have the tread spliced together as far as I know.
I wouldn't recommend running a tire 'against the splice' so to speak because......
On the rear the main force the tire encounters is that of acceleration, even on a relatively low horse power machine.
Stress from braking is minimal on the rear tire, even on a heavy bike.
Of course the front only sees the stress of braking.
A person might get away with running a rear on the front and NOT backwards but...

lain: ?