It's not just 100 farms. It's 100 farms per year based on how many farmers die in that year, using one year as an example.
And most farmers are asset rich on paper, but cash poor in reality. Those combine harvesters that the farmers need to do their work are over £100k on their own. Farmers are not rolling around in spare cash.
There is, however, a few factors that often haven't made the headlines in that the £1m "limit" is on top of the regular IHT brackets, so a couple that own a farm that includes the farmhouse will also be eligible for the uplifted £500k bracket for each of them, so that's another £1m on top.
Here's a farm in Peterborough that's currently for sale - https://www.uklandandfarms.co.uk/rural-property-for-sale/east-anglia/cambridgeshire/36245_lir240108/ - £9,000,000.
Imagine that farm is owned by a family that has been passed on from generation to generation. Current farmer dies. The first £1m of the farm's value is exempt from IHT on the "normal" rules, so £8m is then subject to the new rules. The next £1m is exempt, leaving £7,000,000 with a 50% relief, leaving £3,500,000 taxable at 40% = £1,400,000. (I've probably gone wrong somewhere, but let's say this is a ballpark figure)
For a farm that makes enough for the farmers to live on each year, no-one will have a spare £1.4m knocking around to pay it.
So, assuming the farm is worth £9m, around 15% of the farm will need to be sold to pay the IHT.
Selling a farm takes absolutely ages (someone I know sold part of their farm and it took about 3 years to find a buyer) but the IHT needs to be paid within 6 months of death, so not sure where that's going to come from.
Meanwhile, the useable land is now 15% smaller, so less crops are being generated and consequently the new farmer's income is reduced, or, to make ends meet, more likely, prices will go up.
If, as the articles are saying, there are so "few" farms affected, how much does the government expect to raise using the new IHT rules? £2bn. That's not just 100 farms.