When buying full shares, if you’re really getting close to the line on how many you can buy, it just changes to “all” and will force you to buy a fractional, instead of getting whole shares, like you wanted.
Personally, I only want full shares. Makes dividend calculations easier, makes for the prospect of share-for-share transfer possible in the future (if ever implemented, I guess) too.
Not sure if this is specific to T212 ISA, but that’s what I’m using.