it is always interesting to have a different angle to study a problem.
studying where comes the difference in some positions might be enlightening.
but one must consider the following facts
the midgame eval: when more pieces on the board.
the endgame eval: when few pieces on the board.
for example, kingdanger is mostly mg, and not much eg,
and there are bonus such as space which are mg only and not scored as soon as queens are off the board.
others, such as threat on pawns and initiative are mostly eg, etc, etc...
also a quick look at our current piece values will produce some large difference,
a soon as white or black material is different
PawnValueMg = 128, PawnValueEg = 213,
KnightValueMg = 782, KnightValueEg = 865,
BishopValueMg = 830, BishopValueEg = 918,
RookValueMg = 1289, RookValueEg = 1378,
QueenValueMg = 2529, QueenValueEg = 2687,
so it is highly expected that mg and eg totals will be quite different.
the only important value is the final value
which is an interpolation between the 2 according to current nonpawnmaterial mg value
ScaleFactor sf = scale_factor(eg_value(score));
v = mg_value(score) * int(me->game_phase())
+ eg_value(score) * int(PHASE_MIDGAME - me->game_phase()) * sf / SCALE_FACTOR_NORMAL;
v /= PHASE_MIDGAME;