as much memory {as / as is } absolutely necessary

Question

Example:

Explicit variable declaration speeds up the execution of your procedure. Since Visual Basic knows the data type, it reserves only as much memory as is absolutely necessary to store the data.

If I got rid of is and rewrote that sentence like this:

Explicit variable declaration speeds up the execution of your procedure. Since Visual Basic knows the data type, it reserves only as much memory as absolutely necessary to store the data.

Would the sentence be still grammatically correct and equivalent in meaning to the original one? If so, why then did the author who wrote that sentence opt for including is?

Answer 1

Both are correct and don't give place to misunderstandings. Both sound fine to me, but if I had to say it, I'd go with just as; but that's personal preference or habit.

Why did the author use as is? Since both are correct, probably just a matter of preference, too.