Yes, the Elizabeth line will always officially be called the Elizabeth line, never just Elizabeth.
If you were paying attention they announced this six years ago. Yes it's going to look silly on line diagrams and rainbow boards and in tube map keys. Yes it's entirely inconsistent with how all the other tube lines are displayed. It is however entirely deliberate, indeed it's been in the brand guidelines and style guide since 2017 to signify that Crossrail is an entirely different mode. You are not the first person to point out the inconsistency, nor to assume it's an error, nor alone in thinking you would have done it a completely different way.
In this respect it's a bit like the decision to name the last station on the Northern line extension Battersea Power Station station. TfL also announced this six years in advance, but oh my god it didn't stop people thinking they'd spotted a hilarious anomaly for the very first time. That got very tedious after a while, and people pointing out that Elizabeth line shouldn't have line on the end is going to get very tedious too.
Also yes, we know you never liked the name in the first place. Had you been Mayor in 2016 you'd have called it something else... less royalist, more generic, who knows... but you weren't. Admittedly Boris's sycophancy turned into a massive coup yesterday when an elderly lady in a yellow coat came to open the line named after her and validated his choice. But this is not a decision you could ever have influenced, get over it.
So I've posted this today as a way to air the arguments once and then never again. If you feel the need to explain why Elizabeth line is a mistake I invite you to do it now and then forever hold your peace. I'll warn you now that any future comments on this topic will be summarily shifted back to this post and added to the end of the conversation where the argument will continue to silently fester.
Carry on calling it Crossrail if you want - I intend to - but let us never whinge about the 'line' on the end of Elizabeth ever again.