Answering your post. Nope the upper plate was not meant as a step ladder for any boater to climb from behind the motor which seems to be your concern about such ornament useless plate...
The upper plate which is a water deflector plate it's of "extreme importance" with 2 noticeable visual consequences that definitely won't go unnoticed...check pics !!
1-It it were non existing water flow at speed will climb through the front lower leg section and bang against the lower motor portion and divert back out transom, at speed so much water will be diverted that will slow the combo down due to excessive unwanted lower leg drag. Pic 1
2-With current upper plate, if the water flow at speed crosses over the upper plate the motor will achieve an excessive water splash side or over transom, to cure that will need to raise 1-2 notches the bolt on motor and shim or modified the transom height by means of wooden shims along a final fiberglass re work for an eye catching looking. Can anyone imagine the excessive fuel consumption and lower leg's excessive water drag such motor/transom mismatches accounts for as seen in Pic 1 & 2...
WN if you don't post pics, videos about what's going on at your lower leg to enlighten the on line audience, we have nothing to tech discuss...If the motor height at which you have install it pleases you, who am I to state the contrary...
No Motor Owner's Manual that have read and I've read all states that the flow needs to cross under the upper nor the lower plate, it's entirely up to each boater which type of performance wants to achieve while their combos rides at wot a particular water condition and location. Can both describe what's "Top Performance" for each one?
Hey Fazt, what's the point in posting a Yam 30 HP clamp motor if you don't own nor use one, your specialty are narrow plates gap bolt motor for racing, speeding which their particular own installs doesn't equate to clamp motors installs in the least.
Happy Boating