While in this case the jump into the middle of an instruction was not intentional, several decades ago many Microsoft programs for MS-DOS, like their BASIC interpreter, contained frequent intentional jumps into the middle of instructions.
This technique had already been used in many Microsoft programs for CP/M, i.e. for Intel 8080 or Zilog Z80 CPUs.
There were two reasons for the use of such jumps in the middle of instructions. One was to obfuscate the program for disassemblers, which were desynchronized with the instruction stream by such jumps. The other reason is that each such jump usually saved one byte of instruction code in comparison with conventional conditional program structures.
When the program size was still measured in kilobytes, saving even only one hundred bytes by this method was important.
The instruction into the middle of which a jump was performed was usually an instruction that loaded a 16-bit register with an immediate value that happened to be the encoding for some other instruction.
The value loaded into the register was not used. Therefore, when the instruction was entered through its start address, no operation was done, but when it was entered through a jump, some extra instruction was executed.
A typical use case would be at the beginning of a loop, which was entered after initializing a control variable, while whenever the loop was repeated later an extra instruction was executed (corresponding to the immediate value of the register load), to update the control variable. This saved one byte upon the standard loop implementation that uses an unconditional jump for entering the body of the loop in its middle, after the loop initialization.