Until a few months ago, I am absolutely sure in every single train station I had ever been the announcement was something along the lines of "黄色い線の内側でお待ちください".
Then, out of the blue, one day the word 線 became ブロック. If I'm not wrong, I would say that I noticed this mostly at Tokyo Metro stations, while JR seems (thank god) to still be using 線. This is just based on personal experience and I might be wrong.
My question is, why this sudden change? When exactly did it happen? Is there a particular reason why what has always been a "line" needs to become a "block"? More generally, is the choice of a loan word a coincidence? A very wild guess could be that with the approach of Tokyo Olympics loanwords will increase even more and hence that choice.
Anyway, this has been bugging me for a while and I'm just curious to know if there is any specific reason for this change.
PS. My experience so far is only in Tokyo.