What does それはそれでまったく意味が分からん mean in this context?

Question

The situation was describing how the older sister suddenly stopped in front of the gate, staring at the building ahead, with the other sister following suit. Context leading to the sentence in question:

　気が付くと、司までも同じように校舎を見つめている。

　二人して校舎を……。

　当たり前だけど、こんな事はあまりない。

　なんで、通い慣れた学校を今更真剣に眺める必要があるというのだろうか……。

　意味が分からんのでした。

「なんだよー。双子で不気味な連中だなぁ。どうした司まで？」

「あ、なんでもないよ」

「なんでもないって、顔でもないんですが……」

「司……」

「うん、お姉ちゃん……なんだろ、なんか変な感じ……」

「うん……」

「変な感じ？」

　もう一度、校舎を見つめる。

　築年数十年といった感じの建物。

　これと言って物珍しいデザインでもない。

　それと、昨日から何か変わった事などない……。

　実は、同じに見えて、ロボットに変形する様にでもなった……とかなら分かるんだけど……。

　いや……それはそれでまったく意味が分からん。

I thought both 分かる verbs here were talking about the protagonist understanding why they might react that way (them staring at the school), but the last one doesn't seem to fit that. Am I misunderstanding something?

My translations of the last two lines are:

"Actually, if the school started to turn into a robot then I might understand their reaction."

"Well, that doesn't make sense by itself either."

Answer 1

The narrator is trying to explain why they feel something is wrong with the school although it appears to be the same. I think "if the school started to turn into a robot (in front of us)" is not a good translation. ようになった refers to something in the past, so you have to translate it using past perfect subjunctive.

実は、同じに見えて、ロボットに変形する様にでもなった……とかなら分かるんだけど……
(This "something-is-wrong" feeling) would make sense if the school had, say, actually acquired an ability to transform to a robot (last night).

Next, where did "by itself" come from? それはそれで is often translated as "in its own way". (See this and this) Here, it describes that, although their "feeling" is weird, his wild explanation is equally weird.

いや……それはそれでまったく意味が分からん。
No...that's equally nonsensical. (i.e., I tried making a wild guess to explain this feeling, but it is too unrealistic to accept.)