/*** In practice and especially regarding "data", the 8051 can be coded with either "byte sex". However, regarding code store, the 8051 is big endian as can be examined by assembling the expression:
mov dptr,#0ABCDH
This assembles to the following bytes (expressed as Hex).
90ABCD.

***/

I am not sure you are right. Look at ACALL, LCALL, RET and RETI instruction when 8051 is involved with 16 bits manipulation ( push and pop PC on the stack).
The execution chain is the following:

ACALL:

(PC)<--(PC)+2
(SP)<--(SP)+1
((SP))<--(PClow)
(SP)<--(SP)+1
((SP))<--(PChigh)
(PC)<-- page address

It seems the 8051 is a LITTLE ENDIAN machine considering those instructions and care must be done when using jumping with PUSH & RET instructions mechanism.
One must push LOW PC first on the stack.

Regards,
Cristian