Name for misused idioms

I come across many kinds of English mistakes that fall under the heading of misused idioms and expressions. Here’s one I came across completely at random from a gaming forum post.

…the game should have lots of “meat and potatoes” and it doesn’t.
http://us.battle.net/d3/en/forum/topic/17902110041

In the few sentences I can easily tell that the author is a little sloppy with language all around. The context of the thread was about some game designers departing from their motto and not building a lot of depth into recent titles. The motto refer’s to “Bushnell’s Law” and that “All the best games are easy to learn and difficult to master.” The focus here is not about just covering the basic or essential parts.

So it’s pretty apparent to me that just the word meat alone was intended rather than meat and potatoes. The substituted expression changes the meaning although it still makes a certain amount of sense which is probably a big reason for the confusion and why it’s sometimes difficult to prove that the usage was “wrong”.

I have investigated this many times before. Is there a name for this type of error? I am aware of the concept of malapropism but I don’t believe that fits here. And beyond this question if you had any pointers to references on this topic that would be great.

EDIT

While I think I can make a case for the distinction in meaning I see, my purpose was not to split hairs that way. Apparently I chose an example that was a little too grey. Before writing my question I spent a great deal of time pouring over dictionaries to convince myself there was a distinct difference in meaning.

The difference in meaning though was not the point of my question and I thought I had adequately pointed that out. I have no desire to be pedantic about this, it is simply an interesting topic of linguistics that I have tried to explore and I thought that example was interesting enough to use.

EDIT #2

meat and potatoes: ordinary but fundamental things; basic ingredients. (Google)

The sense of meat that I had in mind may have come from the Bible. It did not seem to me to be obscure to hear it with the meaning of depth, weight, substance.

1 And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, as unto babes in Christ. 2 I fed you with milk, not with meat; for ye were not yet able to bear it: nay, not even now are ye able; (1 Corinthians 3:1-2 American Standard Version)

EDIT #3

After studying the subject and several dictionaries I still believe these do not share identical meanings. It’s particularly evident in the adjective forms.

meat and potatoes [https://en.wiktionary.org/wiki/meat_and_potatoes]
n. : 2. (US, informal) The essential part or parts of something.
adj.: 1. normal, average, typical, unexceptional, or nondescript in description

meat [https://en.wiktionary.org/wiki/meat]
n. : 8. (colloquial) The best or most substantial part of something. [from 16th c.]
We recruited him right from the meat of our competitor.‎

meaty [https://en.wiktionary.org/wiki/meaty]
adj.: 4. Substantial.

For the adjective form I find these synonyms for meaty: interesting, thought-provoking, three-dimensional, stimulating; substantial, satisfying, meaningful, deep, profound (Google)

Forgive that I’m belaboring this point. The fact that there is so much potential for the meanings to bleed together is one of the reasons I’m interested in this class of words.