well yes, that's where the element of trickery comes in.
But there remains the question as to why the other party was happy with a lease marked 'draft'.. it could be argued that they were also intending to use a similar defence in the event of an attempt to enforce a clause... i.e it's not clear that they considered themselves bound, we only have their word for that, if in fact they do claim that.
It comes across as very unprofessional to me... for a professional company to use a lease that has no page numbers, no contents page, that isn't signed on every page, and that has Draft all over it... either party can then remove or add pages and claim they were there or not there all along... there doesn't seem to be any way to resove such difficulties... so it woudl be a matter for the courts.
So perhaps there would be a greater onus on the more profesisonal (or experienced) party to ensure these problems don't exist... I believe it could be said that there was an element of trickery on both sides... and only on the leasee's side if he claims he considered himself not bound... he could also claim to have entered the agreement in good faith believing it to be binding, and then all the trickery, or perceived trickery would be on the professionals side.
Overall, it seems that this would be a poor lease if it had been drawn up by a solicitor.
Would a solicitor advise signing such a lease?, or would they insist on page numbers etc, and signing on each page (or else signing a contents page, with the total number of pages on it), and I'd imagine a solicitor would insist on the word Draft being removed. If these things are not done then there is the problem with removing or adding pages.